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A pedophilic disorder is recognized for its impairment to the individual and for the harm it may cause to others. Pedophilia is often considered a side issue and research into the nature of pedophilia is delayed in comparison to research into other psychiatric disorders. However, with the increasing use of neuroimaging techniques, such as functional and structural magnetic resonance imaging (sMRI, fMRI), together with neuropsychological studies, we are increasing our knowledge of predisposing and accompanying factors contributing to pedophilia development. At the same time, we are faced with methodolog-ical challenges, such as group differences between studies, including age, intelligence, and comorbidities, together with a lack of careful assessment and control of child sexual abuse. Having this in mind, this review highlights the most important studies investigating pedophilia, with a strong emphasis on (neuro-) biological studies, combined with a brief explanation of research into normal human sexuality. We focus on some of the recent theories on the etiology of pedophilia such as the concept of a general neurodevelopmental disorder and/or alterations of structure and function in frontal, temporal, and limbic brain areas. With this approach, we aim to not only provide an update and overview but also a framework for future research and to address one of the most significant questions of how pedophilia may be explained by neurobiological and developmental alterations.
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June 2015 | Volume 9 | Article 3441
published: 24 June 2015
doi: 10.3389/fnhum.2015.00344
Frontiers in Human Neuroscience |
Edited by:
Hauke R. Heekeren,
Freie Universität Berlin, Germany
Reviewed by:
Timm B. Poeppl,
University of Regensburg, Germany
Stuart Brody,
Charles University, Czech Republic
Tillmann H. C. Kruger,
Department of Psychiatry, Social
Psychiatry and Psychotherapy,
Hannover Medical School,
Carl-Neuberg-Strasse 1, Hannover
D-30625, Germany
Gilian Tenbergen and
Matthias Wittfoth have contributed
equally to this work.
Received: 15August2014
Accepted: 29May2015
Published: 24June2015
TenbergenG, WittfothM, FrielingH,
PonsetiJ, WalterM, WalterH,
BeierKM, SchifferB and KrugerTHC
(2015) The neurobiology and
psychology of pedophilia: recent
advances and challenges.
Front. Hum. Neurosci. 9:344.
doi: 10.3389/fnhum.2015.00344
The neurobiology and psychology of
pedophilia: recent advances and
Gilian Tenbergen1†, Matthias Wittfoth1†, Helge Frieling2, Jorge Ponseti
3, Martin Walter
Henrik Walter
5, Klaus M. Beier
6, Boris Schiffer
7 and Tillmann H. C. Kruger
1 Division of Clinical Psychology and Sexual Medicine, Department of Psychiatry, Social Psychiatry and Psychotherapy,
Hannover Medical School, Hannover, Germany, 2 Laboratory for Molecular Neuroscience, Department of Psychiatry, Social
Psychiatry, and Psychotherapy, Hannover Medical School, Hannover, Germany, 3 Department of Sexual Medicine, University
Hospital Schleswig-Holstein, Kiel, Germany, 4 Clinical Affective Neuroimaging Laboratory, Medical Faculty University Hospital
Magdeburg, Magdeburg, Germany, 5 Division of Mind and Brain Research, Charité – University Clinic Berlin, Berlin, Germany,
6 Institute of Sexology and Sexual Medicine, Charité – University Clinic Berlin, Berlin, Germany, 7 Division of Forensic Psychiatr y,
Department of Psychiatry, Psychotherapy, and Preventive Medicine, LWL-University Hospital Bochum, Bochum, Germany
A pedophilic disorder is recognized for its impairment to the individual and for the harm
it may cause to others. Pedophilia is often considered a side issue and research into the
nature of pedophilia is delayed in comparison to research into other psychiatric disorders.
However, with the increasing use of neuroimaging techniques, such as functional and
structural magnetic resonance imaging (sMRI, fMRI), together with neuropsychological
studies, we are increasing our knowledge of predisposing and accompanying factors
contributing to pedophilia development. At the same time, we are faced with methodolog-
ical challenges, such as group differences between studies, including age, intelligence,
and comorbidities, together with a lack of careful assessment and control of child sexual
abuse. Having this in mind, this review highlights the most important studies investigating
pedophilia, with a strong emphasis on (neuro-) biological studies, combined with a brief
explanation of research into normal human sexuality. We focus on some of the recent
theories on the etiology of pedophilia such as the concept of a general neurodevelopmental
disorder and/or alterations of structure and function in frontal, temporal, and limbic brain
areas. With this approach, we aim to not only provide an update and overview but also
a framework for future research and to address one of the most signicant questions
of how pedophilia may be explained by neurobiological and developmental alterations.
Keywords: pedophilia, child sexual abuse, functional and structural MRI, neuropsychology, neurodevelopment,
etiology, epigenetic, neurobiology
In the light of frightening and emotionally disturbing sexual oenses against children, experts have
focused more on the level of sexual behavior, referred to subsequently as “oenses,” while not dif-
ferentiating the causes for that behavior in an appropriate and adequate way. Concerning sexual
oending against children, two groups can be distinguished: rst, those who show no sexual pref-
erence disorder, but whom, for various reasons, sexually abuse children. Reasons include sexually
inexperienced adolescents, mentally retarded persons, and those with antisocial personality disorders
(ASPDs), or perpetrators within general traumatizing family constellations, which seek surrogate
June 2015 | Volume 9 | Article 3442
Tenbergen et al. The neurobiology of pedophilia
Frontiers in Human Neuroscience |
partners in children (Rice and Harris, 2002; Greenberg etal., 2005).
ese individuals are most likely diagnosed with various impulse-
control disorders, accounting for their engaging in child sexual
abuse (CSA) without a specic sexual preference for prepubescent
children (Allnutt etal., 1996; Greenberg etal., 2005). Second, there
are those who do display a sexual preference disorder, namely
pedophilia (i.e., the sexual preference for prepubescent minors)
and/or hebephilia (i.e., the sexual preference for pubescent minors)
(Seto etal., 1999).
Although this preference increases the risk of engaging in CSA,
only about 50% of all individuals who do sexually abuse children
are pedophilic (Blanchard etal., 2001; Schaefer etal., 2010) and
not every pedophilic individual actually has abused children. e
other 50% of individuals that have abused children are those who
do so without a sexual attraction to children; i.e., they lack the
necessary social skills to develop and maintain emotional and
sexual relationships with appropriately aged peers and look to
“replacement partners” in children as a kind of “surrogate” (Beier,
1998; Seto, 2008; Mokros etal., 2012b).
Overall, there is great consensus regarding the negative con-
sequences for victimized children. e number of known cases
of CSA in Germany, for example, was on average 14,600 in the
last 5years (Bundeskriminalamt, 2012). e estimated incidence
is far greater than what is reported to authorities. In the United
States, the National Center for Victims of Crimes, as reported
in Finkelhor etal. (2009), states that one in 5 girls and one in
20 boys are victims of CSA (Crimes, 2012). Additionally, CSA
has important economical aspects. e estimated burden for the
particular countries is enormous, including childhood health care
costs, adult medical costs, productivity losses, criminal justice
costs, and special education costs, which results in an estimated
lifetime cost per victim of non-fatal child maltreatment in general
of $210,000 in the USA (Fang etal., 2012).
In this article, we discuss pedophilia with a focus on recent
ndings of the denition, neuropsychology, and neurobiology
(including neuroimaging) of pedophilia as a specic phenotype
within the spectrum of human sexual preference. For that purpose,
the article highlights the current gaps in literature and oers sug-
gestions as to where the eld of pedophilia research should head
in order to close these gaps.
Pedophilia and Pedophilic Disorder:
A Psychological Perspective
Classication of Pedophilia
Pedophilia is dened as an ongoing sexual attraction toward pre-
pubertal children (Freund, 1963, 1967; Seto, 2009). In the new
DSM-5, pedophilia is de-pathologized by dierentiating between
the sexual preference for prepubescent children (i.e., pedophilia)
and the disorder in case of additional factors. ese factors include
experiencing signicant distress and impairment by fantasies and
urges, or the acting out on behavioral level, including child pornog-
raphy consumption and/or committing hands-on CSA oenses.
e estimated prevalence leads to questions about the diagnos-
tic validity and reliability of pedophilia as a classication entity.
According to the DSM-5, pedophilic sexual preference and the
pedophilic disorder must be dierentiated. As can be seen in
Table1 , the behavioral criterion was not included in the DSM-5 as
a specier, though it holds relevance for researchers and clinicians.
From a clinical point of view, both child pornography consump-
tion and/or hands-on CSA oenses would count as preference
behaviors (Seto, 2010; First, 2011).
From a clinical perspective, it is necessary to stress that there
are pedophilic men who restrict their desire for sexual contact with
children to fantasies only, and other men who are at risk to commit
an oense because fantasy alone does not satisfy their sexual desire.
is second group is potential oenders who wish to reduce their
increasingly overwhelming impulses with therapeutic help (Beier
etal., 2009a,b; Schaefer etal., 2010; Wakeeld, 2012). It is possible
for these men to be diagnosed with Pedophilic Disorder – due to
experiencing interpersonal distress – without them committing
an oense.
e other group of pedophilic men includes those who have
committed sexual oenses against children. ese individuals may
feel remorse (and seek help to avoid a relapse), while others do
not. Note that both fulll criterion B of the DSM-5, as shown in
Table1 , means that it has to be diagnosed as Pedophilic Disorder.
Furthermore, it is necessary to distinguish between the exclusive
type of pedophilia (attracted only to children) and non-exclusive
type, and whether the person is attracted to males, attracted to
females, or to both.
It is a completely dierent situation for perpetrators who com-
mitted sexual oenses against children, which were not caused
by a pedophilic preference. ose are the surrogate types of sex
oenders and can be diagnosed within the category of impulse-
control disorder, accounting for the lack of a sexual preference for
children but the committed act of CSA (DSM-5: 312.89; ICD-10:
63.8). Moreover, most sexual assaults happen in the “Dunkelfeld”
for approximately every reported case of CSA; another ve are le
unreported, suggest some scholars (Hall and Hall, 2007; S eto, 2009).
Dunkelfeld is a German word that literally translates to “dark eld.
It is of great importance for clinical diagnosis whether or not an
erotic preference for the body scheme of children on the fantasy-
level exists. ere is a high chance that this information would be
given voluntarily by self-referred, self-motivated pedophilic men,
but less likely by those who are already involved with the legal
system (probation etc.). It is therefore essential for the assessment
TABLE 1 | Diagnostic criteria of a pedophilic disorder according to
DSM-5 pedophilic disorder
Over a period of at least 6months, recurrent,
intense sexually arousing fantasies, sexual
urges, or behaviors involving sexual activity with
a prepubescent child or children (generally age
13years or younger)
Specify if:
Sexually attracted to males
Sexually attracted to females
Sexually attracted to both
The fantasies, sexual urges, or behaviors cause
clinically signicant distress or impairment in
social, occupational, or other important areas of
Specify if:
Limited to Incest
The person is at least age 16years and at
least 5years older than the child or children in
Criterion A
Specify type:
Exclusive type (attracted only
to children)
Non-exclusive type
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and a reliable diagnosis to obtain a cooperation/compliance level.
In self-motivated pedophiles, this collaboration is highest and
makes them a highly interesting target group for research (see
Section “Methods for Diagnosing Pedophilia”).
is underlines that pedophilia as a sexual preference must
be seen independently from sexual oending against children –
otherwise there would be only oending pedophiles. From a
research point of view, it is imperative to understand in what way
the neurobiological conditions – notwithstanding sexual prefer-
ence – encourage the sexual behavior. ese are possibly the same
mechanisms that also encourage oense-like behavior in men with
other sexual preferences (for instance in the case of rape on the
background of sexual preference for adult women). Additionally,
research eorts have to unravel which neurobiological mechanisms
determine and regulate sexual preference, and how preference and
behavior are interconnected.
In the research domain, pedophilia is currently viewed as a phe-
notype of sexual preference within the realm of human sexuality,
including various dierent phenotypes (e.g., the sexual orientation
toward the same gender), only that it concerns a preferred age in
addition to gender (Beier etal., 2009a,b; Schaefer etal., 2010).
is is separate from, but in addition to, behavioral manifestations
including the use of child pornography and the commitment of
child sexual oenses (Beier etal., 2009a,b; Neutze etal., 2011).
Consequently, the sexual preference itself cannot be considered
a mental disorder similar to how a homosexual orientation was
considered in the 1970s in the United States of America (Green,
2002). Separating sexual preference from psychosocial impair-
ment, thus allowing for the practice of various sexual behaviors
with consenting partners, has been applied within the new DSM-5
with the other paraphilias as well, including fetishism, bondage/
dominance-sadism/masochism, and is therefore not specic to
pedophilia (Wright, 2010, 2014).
Epidemiology of Pedophilia
e most commonly asked question about pedophilia is how
frequently it occurs. Obtaining reliable incidence numbers of
pedophilia as a preference disorder is dicult as individuals are
typically unwilling to admit pedophilic preferences, particularly
when oenses have been committed. e prevalence of a true
pedophilic sexual preference is approximately 1%, but when
general fantasies are investigated, that prevalence can reach up to
5% among men in the general population, extrapolated from the
studies discussed below.
Some studies suggest that the prevelance of pedophilia may
be between 3% and 5% in the general population (as reviewed by
Seto, 2009). In penile plethysmography studies of men with sexual
oense histories against children, these prevalences can jump from
30% for men with one oense to 61% for men with 3 or more sexual
oenses against children (Blanchard, 2010; Seto, 2009).
A rst population-based study concerning this issue was based
on the Berlin Male Study (BMS), in which the prevalence of erectile
dysfunction, its age-dependency, and its relation to general health
variables as well as quality-of-life measures were determined in
6000 men, aged 40–79 (Schäefer etal., 2003; Englert etal., 2007).
A total of 1915 men took part in the rst phase of this study. ese
men were then invited to further participate in a comprehensive
sexological study by responding to an extensive questionnaire on
sexual experiences and behavior. e outcome was a sample of
373 men, of whom 63 were single and 310 were in a relationship.
Fiy-seven percent of the questioned men recognized at least one
paraphilia-associated arousal pattern as part of their fantasies,
46.9% of this group used them for arousal enhancement during
masturbation, and 43.7% acted out these patterns in a relationship.
e nding of relevance here is that 3.8% acted out a pedophilic
preference on the behavioral level – which means of these men – 14
men acted out their impulses toward children. Taking these 14
cases into account, the prevalence of a pedophilic sexual preference
in Germany can be extrapolated to approximately 3.8% in the worst
case (calculated based on the selected sample of 373 men) (Ahlers
etal., 2011). However, pedophilia was not strictly assessed in this
sample; thus, this prevalence should be interpreted with caution.
Much higher is the prevalence in an older anonymous self-
report survey study of 193 healthy male college students: 21%
admitted some degree of sexual interest in children, 9% admitted
to having sexual fantasies involving children, 5% admitted to
masturbating to orgasm through these fantasies, and 9% admitted
that they would have sex with a child, if it were guaranteed they
would never be caught (Briere and Runtz, 1989). Yet, it is important
to note that this study did not specically investigate the preference
of pedophilia, rather sampled fantasy.
Considering the lack of reliable estimates of the prevalence of
pedophilia in general, prevalence estimates for the subtypes of
pedophilia also remain scarce. e current estimated prevalence
of homosexual pedophilia is anywhere between 9 and 40% (Hall
and Hall, 2007); the ratio of heterosexual to homosexual pedophiles
was approximately 1.4:1 among men with CSA oenses in another
study using phallometry (Freund and Watson, 1992). Prevalence
estimates of bisexual pedophilia are not yet available due to meas-
urement complexity (Hall and Hall, 2007).
Although pedophilia is generally regarded as a phenomenon in
males (Seto, 2008), victim surveys show that a female perpetrator
was indicated by between 14 and 24% of sexually abused males
and by between 6 and 14% of sexually abused females (Green,
1999). In a Dutch report (Wijlman et al., 2010) investigating
female sex oenders in the Netherlands between 1994 and 2005,
common characteristics included intellectual impairment, a high
current and/or lifetime prevalence of psychiatric or personality
disorders, and a high lifetime prevalence of neglect and sexual
abuse. Frequently, the abuse against a child is carried out in col-
laboration with a male partner or victims are seen as surrogates
to replace less than desirable relationships. Currently, there is no
reliable estimate of pedophilia in women and the question remains
whether pedophilia, as currently dened, even exists in women.
Methods for Diagnosing Pedophilia
e most important method for ascertaining the phenotype of
sexual preference is the clinical exploration. In this process, the
content of sexual fantasies during masturbation is particularly
signicant as it reveals gender preferences, body scheme age of
the “partner,” and favored practices. Here, it is possible to assess
the sexual preference structure in detail including the dierentia-
tion between exclusive and non-exclusive types of pedophilia and
hebephilia (Beier etal., 2013). If the legal system is involved, the
patient might not (or only partially) cooperate due to the possibility
of new accusations.
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For assessment of body scheme age preference, the ve Tanner
stages have proven useful. ey describe the process of physiologi-
cal maturing by focusing on the development of the secondary
sex characteristics from 1 (prepubescent) to 5 (adult). erefore,
Tanner stage 1 concerns the prepubescent developmental phase,
displaying a complete lack of secondary sex characteristics showing
no facial or pubic hair, no penile or scrotal enlargement in males,
no breast development or pubic hair growth in females. Tanner
stage 2 corresponds to the onset of breast budding in females and
testicular enlargement in males. Tanner stage 3 depicts the breast
and areola development in females, continued testicular growth
and initial penile lengthening in males. Tanner stage 4 corresponds
to increased breast and areola growth, initial separation from sur-
rounding breast tissue in females, and in males testicular volume
increases, scrotum darkens, penile elongation continues. Tanner
stage 5 represents full maturity, complete breast development, and
separation from surrounding breast tissue in females, full penile
growth and scrotum darkness, and testicular volume in males, and
full pubic hair coverage in both (Marshall and Tanner, 1969, 1970).
Please refer to Figure1 for a visual explanation of Tanner stages
and their relationship to sexual preference. e Tanner stages can
be very useful during the exploration of sexual preference and are
an essential component of the diagnostic procedure in various
treatment and research programs (Seto, 2008). Pedophilia is here
dened as the erotic attraction to a prepubescent body scheme
corresponding to Tanner stages 1 and 2 (Blanchard, 2010).
Child pornography use is also strongly related to pedophilia. As
a study deriving from the German Dunkelfeld Prevention Project
FIGURE 1 | Tanner scales of males and females as used in sexual
preference assessment. Image credit: Michał Komorniczak, 2009,
CC-BY-SA. Tanner Scale Male: Tanner Scale Female:, both accessed June 09, 2015.
concluded, among 345 pedophiles admitting one or more sexual
oenses against children, 37% have solely used child pornography,
21% committed exclusively hands-on sexual contacts with a minor,
and 42% have committed both (Neutze etal., 2012).
e most well-known objective method of measuring pedo-
philic interest is penile plethysmography (PPG) or phallometry.
is method measures genital sexual arousal through sexual
stimuli and is based on the relative change in penile response.
Sexual preference can be determined as the relative change in
penile response to various classes of sexual stimuli (according to
Tanner scales), such as prepubescent, pubescent, or adult, female,
or male targets. At least one of these classes should correspond to
the individual’s stated or inferred sexual preference. ere are two
dierent methods of phallometry, circumferential and volumetric.
e circumferential method measures intra-individual changes in
penile girth through a wire band tted around the base of the
penis in response to diering classes of sexual stimuli (Ba nc ro 
etal., 1966). e volumetric method uses a glass tube tted around
the penis to measure calibrated air output as a result of erection
(Freund, 1963). e latter method is sensitive to small changes,
making it useful when assessing partial- or non-admitters, or pedo-
philic men that attempt to hide their sexual preferences (Freund
and Blanchard, 1989; Blanchard etal., 2001). Both measures are
valid and reliable, producing sensitivities between 55 and 61% and
specicities between 95 and 96% (Kuban etal., 1999; Blanchard
etal., 2001; Hughes, 2007).
Self-reported interest in children, child pornography use, and
the number of children as sexual victims all uniquely contribute to
phallometrically assessed sexual interest in children (Mokros etal.,
2012b). Additionally, child pornography users showed a greater
phallometric response to sexual child stimuli than non-pedophilic
child sexual oenders (CSO), and there was no signicant dier-
ence within the child pornography group between those who had
committed sexual oenses against children and those who had
not (Seto etal., 2006).
While phallometry has long been the ‘gold standard’ in assess-
ing sexual preferences, other methods have been developed using
indirect and implicit tests to cope with faking responses. One of the
more strongly validated tests is the viewing time paradigm meas-
uring the length of time a participant spends looking at specic
images as an indicator for sexual preference. Research assumes that
all participants, including CSO, will look signicantly longer at
sexually arousing stimuli (Mokros etal., 2012a). An initial study by
Abel showed a high specicity and sensitivity to classifying sexual
oenders against adolescent boys (98% control vs. 90% oender),
only moderate sensitivity for those against boys under 14 (98 vs.
76%), and lower performance against adolescent/young girls (77
vs. 91%) (Abel etal., 1994). A follow-up study found that between
the viewing time paradigm and the PPG, discriminatory capacity
was negligible, showing no signicant dierences in their abilities
to discriminate among sex oenders with deviant sexual interest
in adolescent females, adolescent males, female children, or male
children (Abel etal., 1998). Abel etal. (1998) suggested, however,
that the PPG may be slightly better at classifying oenders against
young boys, although this claim needs urgent replication.
e pictorial Stroop was developed as a modied, sexual version
of the original Stroop task, measuring implicit sexual associations
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Tenbergen et al. The neurobiology of pedophilia
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that exert their eects automatically, which are dicult if not
impossible to control consciously. Research supports its use among
a sample of CSO (n=24) compared to controls (n=24), with those
admitting deviant sexual interest in children having the greatest
mean bias for child stimuli as compared to adult stimuli (partial
η2=0.07) (Ciardha and Gormley, 2012). However, other factors
could have contributed to the results, justifying a need for further
renement. Results in a separate study of 35 men, 11 of who were
homosexual and 24 were heterosexual, reporting no history of
child sexual oenses indicated a discriminatory ability between
heterosexual men and homosexual men using female stimuli,
but could not discriminate among preferred ages. e authors
suggested that other mechanisms are responsible for rating child
stimuli, thus decreasing the validity for this test among pedophilic
participants (Bourke and Gormley, 2012).
Eye tracking and pupil dilation may also indicate sexual prefer-
ence and results show that men react more strongly in these studies
than women. Heterosexual men did initially orient to their stated
preference and eye xations were signicantly longer than when
looking at non-preferred stimuli (Fromberger etal., 2012b). In a
study investigating pedophilia, eye tracking produced high sen-
sitivity and specicity, 86.4 and 90.0%, respectively (Fromberger
etal., 2012a). Heterosexual women reacted similarly to stimuli
of both sexes, whereas heterosexual men, homosexual men, and
homosexual women reacted most strongly to their stated partner
gender in pupil dilation research (Rieger and Savin-Williams,
2012). However, criticisms have been put forward suggesting that
the success seen in heterosexual and homosexual participants to
respective stimuli in pupil dilation studies is attributable to factors
other than sexual preference, such as luminance, salience of the
stimuli, and emotional reaction (Beatty and Lucero-Wagoner,
2000; Rieger and Savin-Williams, 2012). ese methods have not
yet been used in the sexual age preference measurement of pedo-
philes, but do hold promise as collateral information for diagnosis.
e aforementioned methods are not without their aws,
such as test–retest reliabilities or the ability to fake results. ese
methodological dierences have led to interest of using specic
functional Magnetic Resonance Imaging (fMRI) techniques in
order to classify pedophilic interest (Ponseti etal., 2012). Results
have shown that a preference-specic BOLD pattern is evident,
which can be potentially used as a diagnostic tool. Keeping these
ndings in mind, this methodology could be used in the future
as a classication paradigm.
Co-Morbidities with Pedophilia
Pedophilia does not always occur in isolation; men with pedophilia
oen have extensive histories of psychiatric disorders that, in
extreme cases, can overshadow discovery of etiological course.
Whether this is a secondary phenomenon that relates to emotional
and social consequences of this preference, or whether these are
true co-morbidities remains elusive.
Kramer (2011) addresses a point that currently many pedophilia
researchers are facing: should we continue to classify pedophilia
as a separate psychiatric disorder or as a sexual orientation, when
patients harbor complaints not only of the preference but of the
pressure under which they suer? is pressure oen precedes
the onset of psychiatric illness (most oen mood or anxiety
disorders), which then precedes the decision to seek psychiatric
help (Kramer, 2011). Due to a temporal-causal relationship being
nearly impossible to determine in these cases, the DSM-5 has
dierentiated among those who experience the sexual preference
but do not suer and those who do, leading us back to Pedophilia
vs. Pedophilic Disorder, regardless of whether or not child sexual
oenses have occurred (Kramer, 2011).
A relationship has been identied between pedophilia and co-
morbid psychiatric disorders. Among pedophiles in residential or
outpatient treatment, two-thirds had a lifetime history of mood or
anxiety disorders, 60% had lifetime substance abuse history, with
51% naming alcohol as their drug of choice, and 60% qualied for
a personality disorder diagnosis of which obsessive-compulsive
(25%), antisocial (22.5%), narcissistic (20%), and avoidant (20%)
were most common, as reported in reviews (Fagan etal., 2002;
Green, 2002). Kalichman (1991) investigated 144 sexual oenders
divided into child, adolescent, and adult oenders (although not
controlled for pedophilic preference) for state and trait measures of
anger, anxiety, self-esteem, and various measures on the Minnesota
Multiphasic Personality Inventory (MMPI). Findings demon-
strated that child oenders, as compared to oenders against
adolescents and oenders against adults, scored signicantly
higher on 2 out of 3 scales for the “neurotic” triad (hypochondriasis
and hysteria), and 3 out of 4 scales for the “psychotic tetrad” (para-
noia, psychasthenia, schizophrenia), and were signicantly more
introverted (Kalichman, 1991). ese ndings suggest that child
sexual oending is characterized by emotional disturbance and
higher rates of psychopathology. Moreover, these ndings do not
necessarily mean that there is a direct connection to pedophilia.
In an empirical study comparing 20 forensic inpatients with
pedophilia attracted to males or attracted to females (but lacking
information of whether they were exclusive or non-exclusive types,
respectively) and 24 matched male controls on various psychiatric
measures, ndings included increased personality subscale scores
from the MMPI-2 for psychopathy and paranoia, with enhanced
scores for hypochondriasis, depression, hysteria, and masculinity/
femininity, psychasthenia, schizophrenia, and social introversion
(Kruger and Schier, 2011). Furthermore, that study shows that
61.1% of the sample qualied for a personality disorder diagnosis,
with Borderline Personality Disorder (22%; from Cluster B) and
Avoidant Personality Disorder (33%; from Cluster C) as the two
most common (Kruger and Schier, 2011). Self-report results in low
socioeconomic status individuals, oen including non-pedophilic
sexual oenders against children and rapists, indicate more social
anxiety, less social poise, and a decreased ability to appropriately
socially assert oneself, relating to the cognitive distortions seen
among these groups of negative attitudes toward women, reinforc-
ing beliefs about sex with children, denial of harm to victims, and
misattribution of responsibility of oending (Geer etal., 2000).
ese results indicate that delinquent pedophiles seem to
dier from healthy controls (HC) for Axis I and II psychiatric
comorbidity development. However, it remains to be further
explored whether these alterations are linked specically to the
sexual preference of pedophilia or to the commitment of sexual
oenses against children, as meant by the behavioral criterion of
Pedophilic Disorder (impaired control over sexual impulses) or
a combination of both.
FIGURE 2 | Overview of neuropsychological ndings in pedophilia and
child sexual offending.
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Neuropsychological Findings Associated with
Aside from psychiatric comorbidities, neuropsychological altera-
tions are another important issue, which have been addressed by
several studies, and may further contribute to the understanding
of the development and course of pedophilia. e majority of stud-
ies in the following paragraphs were conducted as uncontrolled
studies, mostly using incarcerated CSO, which were not carefully
screened for incarceration stress or for pedophilic sexual prefer-
ence. erefore, the results are not generalizable and need careful
Initial studies exploring the neuropsychological correlates of
pedophilia oen used uncontrolled designs with incarcerated
pedophilic men. An initial study by Tarter et al. (1983) among
recently incarcerated adolescent oenders and controls, no
neuropsychological dierences were found among the groups on
the Wechsler Adult Intelligence Scale (WAIS) or Pittsburgh Initial
Neuropsychological Test System. Furthermore, among incarcerated
adult male sex and non-sex non-violent oenders, no dierences
were seen in any neuropsychological test variables, aer age and
education status were accounted for (Abracen etal., 1991). Keeping
in mind that the subject groups were incarcerated at the time of
study and that pedophilia was not explicitly examined, the results
are limited in their generalizability and specicity to pedophilia.
In another study, heterosexual and homosexual pedophiles were
tested, but each group, plus one control group, had sexual oense
histories and were incarcerated at the time of the study. Fully admit-
ting, heterosexual pedophiles had gender dierentiation indices
(or the erotic sensitivity for the gender-dierentiating body shapes
that distinguish physically mature males and females), which were
greater than for non-admitting heterosexual pedophiles, but no
dierences were found for either homosexual or bisexual pedo-
philes. is highlights that fully admitting heterosexual pedophiles
prefer the body shapes of female children, whereas the partial- or
non-admitting pedophiles do not seem to discriminate between
victim body types (Freund etal., 1991; Freund and Kuban, 1993).
Gillespie and McKenzie (2000) investigated neuropsychological
dierences among forensically incarcerated sex oenders and
non-sex oenders and found no signicant dierences on any
of their measures, including the WAIS, Trail Making Task, List
Learning test, Controlled Oral Word Association test, and National
Adult Reading Task (NART). Among personality disordered
oenders, violent sex oenders, violent non-sex oenders, and
non-violent, non-sex oenders, no dierences were noted on
any neuropsychological test variables, including the WAIS, Trail
Making Task, Face Recognition, Wechsler Memory Scale-Revised,
and Wechsler Recognition Memory Task (Dolan etal., 2002). As
with previous studies, neither incarceration status nor sexual
preference was controlled for, which limits the generalizability
results to pedophilic men.
Within a heterogeneous group of 20 sexual oenders (not dif-
ferentiated by gender or age preference), executive functions were
signicantly impaired; however, the generalization of these nd-
ings to pedophilia is limited considering the nature of the group
(Joyal etal., 2007). Findings included prolonged Stroop eects
(reaction time dierences between incongruent and congruent
trials: 77.2 vs. 59.4s) that were indicative of stronger interferences
and impaired verbal skills, with decits seen in verbal uency and
in verbal processing and memory. While response inhibition and
sustained attention showed impairments, set shiing, cognitive
exibility, and visuo-spatial integration abilities were normal.
In a more controlled study that dierentiated among pedophilic
CSO with a primary sexual interest in prepubescent children
(n=20) and non-pedophilic CSO with a primary sexual inter-
est in adults (n=20) and controls (n=20), Suchy etal. (2009)
investigated patterns of executive function. Non-pedophilic
oenders showed general impairments, whereas among pedophilic
oenders, decits were more specic. Both groups showed decits
in executive functions, specically showing slower information
processing speeds for pedophilic oenders and semantic knowl-
edge impairments in non-pedophiles (Suchy etal., 2009, 2014).
Eastvold etal. (2011) corroborated these results, further specifying
that although pedophilic (incarcerated) oenders (n=30) do not
show generalized executive functioning impairments, they instead
show a distinct pattern of dierences, not all of which are worse
than that for control participants, characterized by impaired per-
formance on behavioral inhibition measures (partial η2=0.129),
but better performance in abstract reasoning measures and plan-
ning measures (partial η2=0.132) as compared to non-sexual
oender (n=29) and non-pedophilic sexual oender controls
(n=30). A further study also found specic decits in inhibition in
15 pedophilic oenders as compared to non-sexual oenders and
non-oender controls, whereas more global executive functioning
impairments were seen in non-pedophilic child molesters (Schier
and Vonlaufen, 2011). Yet, new ndings are showing that pedo-
philic men are characterized by a distinct neurocognitive weak-
ness, performing worse than controls on measures of behavioral
inhibition and information processing (Suchy etal., 2014), but
do not have a more planning-oriented response style as found by
Eastvold and colleague (Habermeyer etal., 2013b). Please refer to
Figure2 for an overview of neuropsychological impairments seen
in non-pedophilic and pedophilic child sex oenders.
Despite these results, further research has indicated contra-
dictory results regarding executive functioning impairments.
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For example, heterosexual formerly incarcerated pedophiles
scored lower than controls in the Wechsler Adult Intelligence
Scale-Revised (WAIS-R) vocabulary subtest measuring verbal
fluency, but performances on tests measuring impulsivity or
attention capabilities were all normal: Wisconsin Card Sorting
Task (WCST), Trail Making Task A and B, Gambling Test, Stroop
Color-Word Test, and Controlled Oral Word Association test
(Cohen etal., 2002). In a study using a shortened version of the
WAIS-R known as the WIP, the WCST, the d2 Attention Deficit
Test, and the Corsi Block-Tapping Test showed that – unlike the
Cohen study (Cohen etal., 2002) – convicted pedophiles serving
prison sentences in a forensic treatment facility had impaired
performance on all subtests of the WIP except for completing
images (Kruger and Schiffer, 2011). The participants consisted
of both exclusive heterosexual and homosexual pedophiles.
Significantly weaker performance on the d2 Attention-Deficit
Test was also seen, but this difference disappeared once par-
ticipant age was controlled. The Corsi Block-Tapping test and
the WCST, however, showed normal performances among the
pedophilic offender group. Cantor etal. (2005), in their meta-
analysis of IQ data in sex offenders, found not only that lower
IQ between 90 and 95 was associated with sexual offending
against children and with pedophilia specifically, but also that
the younger the victim, the lower the IQ of the offender.
ese results suggest that disturbed and prosecuted pedo-
philes do show decits in executive functioning, which might be
due rather to mental disturbances and not to the sexual prefer-
ence. is is in contrast to ndings from the APSD/psychopathy
literature that suggests, at least among community samples
measured for psychopathic traits, that these personality traits
are linked to decits in response inhibition and impulsivity,
specically with social deviancy associated with overall decits
in executive functioning and response inhibition, whereas
callous-unemotional traits observed in psychopathy are asso-
ciated with improved executive functioning abilities (Sellbom
and Verona, 2007). In ASPD, broad executive function domain
decits have been noted in response inhibition, planning, and
rule acquisition, and reversal learning, suggesting that previous
studies examining pedophilia may have been measuring ASPD
or simply an incarceration stress eect in their incarcerated
samples rather than pedophilia. is is in contrast to recent stud-
ies that have found processing speed impairments in pedophiles,
but few other decits suggestive more of oense status eects
than sexual preference eects (Eastvold etal., 2011; Kruger and
Schier, 2011; Schier and Vonlaufen, 2011; Suchy etal., 2014).
Future studies need to carefully control for psychiatric comor-
bidities, incarceration status, and oender status, as no research to
date has examined neuropsychological decits in potential oend-
ers or non-oending pedophiles. Only with these studies will the
true nature of neuropsychological impairment be illustrated.
Neurobiology and Neurodevelopment of
Introduction and Conceptual Framework
Research regarding the etiology of pedophilia suggests the view of
a complex and multifactorial phenomenon in which the inuences
of genetics (Blanchard etal., 2007), stressful life events, specic
learning processes (Jespersen etal., 2009a), as well as perturbations
in the structural integrity of ‘pedophilic’ brains may generate this
specic phenotype of a sexual preference (Schier etal., 2007;
Schiltz etal., 2007; Cantor etal., 2008). Initial theories relied mainly
upon psychological mechanisms to account for a pedophilic
preference, including classical and operant conditioning, as the
behavioral mechanism through which the ‘abused-abuser’ theory
by Freund etal. (1990) and Freund and Kuban (1994) could be
explained as well as attachment style in childhood as a marker
for dysfunctional cognitive sexual schemas in adulthood (Beech
and Mitchell, 2005).
e rst theories to account for sexual behavior disorder associ-
ated with pedophilia suggested masturbatory conditioning [e.g.,
Laws and Marshall (1990)] or childhood sexual abuse (Freund
etal., 1990; Fedoro and Pinkus, 1996) as causal explanations.
However, as Seto purports, due to lack of stringent methodol-
ogy that includes proper control groups, small experimental or
treatment eect sizes, and lacking knowledge of eect duration,
these theories are not well supported. Beyond this, the majority of
victims are female, whereas the majority of oenders are male, and
if conditioning were the only logical theory to explain the etiology
of pedophilia, it stands to reason that there would be more female
pedophiles than are clinically seen (Seto, 2008; Jespersen etal.,
2009b). However, a study by Klucken etal. (2009) showed that men
are more easily conditioned through exposure to sexual stimuli
than are women, casting signicant doubt on the conditioning
theory as it applies to female pedophiles. Currently, there is a
strong push to understand the brains role in sexual preference
development, particularly as it relates to pedophilia.
As discussed in a previous review by Seto (2008), there are
three major neurobiological theories, which have come to be
connected to pedophilia but all have the same shortcoming that
they rely on data based on cases of pedophiles who have other
psychological disorder diagnoses, are incarcerated or otherwise
legally sanctioned, or are not suciently diagnostically classied
(i.e., not dierentiating between the exclusive or the non-exclusive
type, etc.).
e rst is the “frontal lobe” theory that refers to orbitofrontal
and le and right dorsolateral prefrontal cortex dierences that are
oen seen in pedophilic men (Graber etal., 1982; Flor-Henry etal.,
1991; Burns and Swerdlow, 2003; Schier etal., 2007, 2008a,b).
As the orbitofrontal cortex is responsible for behavior control
(Bechara etal., 2000; O’Doherty etal., 2003), especially inhibiting
sexual behavior, volume dierences or dysfunction in this area may
explain the sexual behavior disorder associated with pedophilia,
although not pedophilic sexual preference.
e second major theory is the “temporal lobe” theor y, referring
to reports of hypersexuality accompanying pedophilia. Studies
have shown that disturbances of the temporal lobes can result in
an increase in pedophilic behaviors or an increase in the breadth of
deviant sexual interests (Hucker etal., 1986; Langevin etal., 1988).
ese disturbances include temporal lesions and hippocampal
sclerosis (Mendez etal., 2000). Ponseti noticed further dieren-
tial temporal lobe activations in pedophilic men that highlight
a hypersexuality-specic activation prole, further supporting
the role of the temporal lobe in the expression of hypersexuality
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that is oen seen with sexual behavior disorders (Schiltz etal.,
2007; Ponseti etal., 2012). However, this t heory also does not fully
explain the etiology of the preference.
e third major neurobiological theory holds that dierences
in the sex dimorphic brain structures aected by the masculini-
zation of the male brain would more strongly aect pedophilia
development. Furthermore, the volumes of these structures would
be inuenced, but the hypothesis failed to state in what direction
these changes occur, i.e., either increased or decreased volumes as
a result of testosterone exposure. In the frontal and temporal lobes,
these dierences would be limited to those sexually dimorphic
structures, rather than a generalized dierence in region volume,
but research has not supported the hypothesis (Cantor etal., 2008).
Furthermore, there is an additional theory that combines the
frontal and temporal lobe theories. It states that the frontal and
temporal lobes aect pedophilic sexual preference expression
and its associated behaviors dierently, with the frontal lobe
(orbitofrontal and dorsolateral prefrontal cortices) accounting for
committing the sexual oenses against children and the temporal
lobe (amygdala and hippocampus) accounting for the sexual
preoccupation with children oen seen in pedophilic men (Seto,
2008, 2009; Poeppl etal., 2013).
Currently, pedophilia is oen viewed as an interaction among
neurodevelopmental factors based on genes and the (inutero-)
environment as previously discussed (Becerra García, 2009). is
theory holds that pedophilic sexual preference is a neurodevel-
opmental disorder corroborated by increased rates of non-right-
handedness, shorter stature, lower intelligence, head injury,
prenatal androgen levels, and the associated neuronal structural
and functional dierences that are present since childhood and/
or adolescence. e exact directions of these relationships to
pedophilic sexual preference, committing child sexual oenses,
or consuming child pornography are still to be disentangled. ere
is currently no causal evidence yet to support a role in pedophilic
sexual preference development.
Neurodevelopmental Correlates of Pedophilia
e prevailing perspective among biologists was that sex dier-
ences are linked solely to the exposure to testosterone inutero [see
Phoenix etal. (1959) and Ehrhardt and Meyer-Bahlburg (1979)].
e masculinization of an initially undierentiated human female
brain is caused by testosterone’s induction of organizational eects
during a limited period of time, as extrapolated from animal
research. Sexual dierentiation and development of subsequent
sexual preference are likely an interplay between the impact of
sex chromosomes on gene expression and sex hormones (Bao
and Swaab, 2010). In pedophilia, research investigating biologi-
cal dierences is underway and studies have already highlighted
structural and functional dierences. e following is a discussion
of ndings that are classied as neuropsychological; however, the
onset of these dierences is inutero, childhood, and adolescence,
thus suggesting that these ndings are actually a part of human
development and contribute to pedophilic preference onset rather
than acting as consequences thereof.
As a group consisting of primarily incarcerated individuals,
pedophilic men show a doubled rate of head injuries before age 13,
though aer 14years of age the dierence is no longer signicant,
highlighting possible causative eects in multiple areas of cognitive
functioning. While prenatal perturbations inuence cognitive
functioning and disorder development, so can head injuries result-
ing in unconsciousness in childhood, especially before age 13years
(Blanchard etal., 2002, 2003). is is a result of cortical develop-
ment plasticity during childhood, when synaptic myelination and
pruning are at their peak (Zhong etal., 2013). Of 725 originally
tested, 685 pedophilic men participated in a study investigating
the role of head injuries with associated loss of consciousness
in pedophilia development. Pedophilic participants reported a
signicantly higher number of head injuries that resulted in a loss
of consciousness prior to age 13 than did non-pedophilic child
sexual oender participants. ese results also positively correlated
with a diagnosis of attention decit-hyperactivity disorder and
le-handedness among pedophilic participants.
More importantly, the more child victims each pedophile had
correlated positively with each additional head injury before age
13, but not those sustained later in adolescence or adulthood
(Blanchard etal., 2003). However, no studies have yet been con-
ducted investigating head injuries in non-incarcerated pedophilic
men with histories of CSA, or those with no such histories. Also
lacking are studies on the prevalence of head injuries in children
in general, as well as for the number of children with head injuries
who subsequently go on to commit sexual oenses against children
in adulthood.
e organizational–activational hypothesis was initially devel-
oped by Phoenix and his colleagues in the 1950s in consequence to
observations that a temporary rise in prenatal and early post-natal
testosterone shapes development by masculinizing and defemi-
nizing neural networks in males, whereas the absence thereof
results in the development of female-typical neural phenotype
(Phoenix etal., 1959; Schulz etal., 2009). According to the organi-
zational–activational hypothesis, pre- and perinatal as well as
pubertal/adolescent androgens are able to shape cortical circuits
(organization), whereas in adults androgens can only modulate
the activity of these circuits (activation). e process of sexual
dierentiation occurs between weeks 12 and 18 of prenatal life
and during the rst 2months aer birth, periods during which
testosterone has organizational eects on the brain. During this
time, not only behavior is programed, depending on the level of
exposure to testosterone, but also handedness, total digit length,
and second to fourth nger length ratios (George, 1930; Rahman,
2005). ese neuroendocrinological developmental dierences
are then activated during puberty and their relationship to
pedophilia development will be discussed further in the coming
In understanding the relationship between testosterone, the
brain, sexual behavior, and the rise of sexual deviancy, one must
rst understand how testosterone inuences the brain. In verte-
brates, androgen receptors (ARs) can be found in several brain
regions, including the lateral septum, posteromedial bed nucleus
of the stria terminalis (BNSTpm), medial preoptic nucleus of the
hypothalamus, ventral premammillary nucleus, ventromedial
nucleus of the hypothalamus, and the medial amygdaloid nucleus,
otherwise found in the temporo-occipital, superior-parietal, and
orbitofrontal cortices (Wood and Newman, 1999; Jordan etal.,
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Research has shown a relationship between prenatal androgen
exposure and hand preference in pedophilic men with a history
of sexual oending against children. ese men show a trend for
increased rates of sinistrality – more ecient use of the le side/
hand and is preferred – whereas hebephilic men show increased
rates of ambiguous-handedness (Fazio etal., 2014) as compared
to teleiophiles, and this has been discussed as an indicator of
developmental perturbations resulting from a lack of prenatal
testosterone exposure (Cantor etal., 2004). Homosexuality has
also been associated with a higher prevalence of le-handedness
(Cantor, 2012), and it would be of interest to see whether the
higher prevalence of le-handedness seen among pedophilic men
is attributable to pedophilia specically or to a higher rate of homo-
sexuality within this population as compared to teleiophilic men.
More specically, approximately 11% of the general non-oender
population is non-right-handed, whereas pedophilic men with
histories of sexually oending against children are approximately
15% non-righthanded, this dierence being signicant (Bogaert,
2001; Cantor etal., 2004, 2005; Blanchard etal., 2007; Rahman
and Symeonides, 2008). Future studies should control for sexual
orientation (homosexuality vs. heterosexuality) when examining
handedness in pedophilia.
ese eects also inuence the second to fourth nger length
ratio (D2:D4) (Voracek etal., 2007), a marker altered also in other
psychiatric disorders including alcohol dependence (Lenz etal.,
2012). e D2:D4 ratio is smaller in men than in women and
is used as an indirect marker of prenatal testosterone exposure
(Beaton et al., 2011). Additional dierences in sexual orienta-
tion exist, such that the D2:D4 ratio is smaller in homosexual
women compared to heterosexual women, as well as homosexual
men compared to heterosexual men (Williams etal., 2000; Rahman
and Wilson, 2003; R ahman, 2005; Manning etal., 2007). Although
prenatal testosterone exposure aects both hand preference and
D2:D4 ratio, the data here are equivocal and no rm conclusions
have been drawn regarding the absolute relationship between hand
preference and D2:D4. However, exposure to prenatal testosterone
does not aect the D2:D4 ratio between 9weeks gestation and
birth, in contrast to hand preference, where dierences are noted
here and possibly aer puberty (Lenz etal., 2012). How this applies
to pedophilia is currently under investigation.
e following markers of neurodevelopmental abnormality
have also been implicated in the neurodevelopmental processes
contributing to pedophilia: sibling sex composition, maternal
and paternal age at birth, and the uctuating asymmetry of nger
lengths and wrist widths. Pedophiles have a greater number of older
brothers (Lalumière etal., 1998; Côté etal., 2002). Greater paternal
age at birth was related to an increased chance of homosexual-
ity, whereas greater maternal age increased risk for pedophilia,
specically (rather than generalized paraphilia) (Rahman and
Symeonides, 2008).
Considering the eects of neurodevelopmental perturbations
and executive functioning on pedophilia development, it seems
worthwhile to consider the eect of intelligence. Research results
have been contradictory: for example, generalized sexual delin-
quency is related to lower intelligence, whereas among groups of
non-sexual oenders, pedophiles, and non-pedophiles, neither
education level nor intelligence diered signicantly. However,
when pedophilic participants were separated by use of child
pornography, those who had no history of child pornography use
showed a decreased IQ and lower mean education level as compared
to those who did (Briken etal., 2006; Blanchard etal., 2007; Schier
and Vonlaufen, 2011). e main caveat to this research is that child
pornography is considered a reliable indicator of pedophilic sexual
interest, therefore confounding any results found with education or
intelligence level because those pedophiles with child sexual oense
histories are also more likely to have used child pornography (Seto,
2010). Research is currently focusing on the role of intelligence
among pedophilic men who have only consumed child pornog-
raphy and those who have committed CSA oenses, particularly
dierentiating those who have been incarcerated from those who
have not (Babchishin etal., 2011; Seto etal., 2011, 2012).
As these results indicate, pedophiles do seem to dier from
HC on neurodevelopmental measures. However, these results
are varied and few strong conclusions can be drawn, including
increased rates of le-handedness and increased rates in head
injuries before age 13. e next section will discuss the relationship
of neurological and neurobiological dierences to the development
of pedophilia, as both are the focus of current research determining
the neural correlates of pedophilia. Please refer to Tab le  2 for a
summarization of neuroimaging ndings in pedophilia.
Structural Brain Alterations in Pedophilia
For the purposes of this review, we focused on providing an over-
view of recent neuroimaging work in pedophilia research starting
in 2007, with case studies from 2000 to 2003. is was done for
space and readability reasons; such that another recently published
review provides an excellent in-depth discussion of neuroimag-
ing in pedophilia (Mohnke etal., 2014). at review summarizes
the state of the art of neuroimaging in pedophilia as being in its
infancy, with a general consensus that ndings are scattered and
need to be replicated. Most results from neuroimaging studies
in pedophilia have found neurostructural or neurofunctional
correlates of CSA, not pedophilia perse. e amygdala remains a
region of high interest, but Mohnke etal. (2014) suggest stricter
methodology to replicate these ndings. Our discussion parallels
and expands upon the aforementioned review.
A famous case study that highlighted a neurological disease
that caused impulsive sexual behavior and could have been an
expression of an underlying pedophilic orientation was a right
orbitofrontal tumor in a 40-year-old man (Burns and Swerdlow,
2003). Prior to the discovery of his tumor, the patient had overtly
claimed no sexual interest in children, but aer the tumor pro-
gressed, he made sexual advances to his prepubescent stepdaughter
and began a pornography collection, including child pornography,
resulting from impulse control loss associated with orbitofrontal
cortex dysfunction. Although his behavior was non-exclusive and
his preference was not explicitly tested, the most striking fact about
his symptoms is that all pedophilia-like symptoms disappeared
aer resection of the tumor. Even more, aer the tumor recidivated,
the pedophilia-like symptoms remerged and disappeared again
aer the second resection, thus showing a clear causal link between
behavior and brain function. However, the clear majority of orbito-
frontal tumors do not result in pedophilic behavior, meaning this
case study should be interpreted cautiously.
TABLE 2 | Findings from previous neuroimaging studies in pedophilia.
Method Structural/
PPT groups (n) Paradigm/
Correction Threshold/
etal. (2007)
MRI Frontostriatal
and cerebellum
Heterosexual (9)
and homosexual
pedophiles (9)
brain/SPM 2
FDR (whole
corrected within
p<0.05 GM volume reductions in pedophiles: PHc L/R,
IFG L/R, OFC L/R, Ins L/R, Cer L/R; Cin L/R,
Posterior Cin L, STG L/R, MiTG R, Pcu L/R, Put
L/R (Amy L/R in unpublished re-analysis)Heterosexual (12)
and homosexual
(12) controls
Schiltz etal.
MRI Amygdala
Pedophilic (15)
controls (15)
for multiple
within ROIs
p<0.05 GM reductions in pedophiles: Amy R, Hyp L/R, SI
L/R, Septal Region R, Bed Nucleus
Striae Terminalis L/R
Enlargement of Temporal Horn R
Poeppl etal.
MRI Prefrontal cortex
and amygdala
Heterosexual (2)
and homosexual (7)
toolbox/SPM 8
FWE corrected
within ROIs
p<0.05 GM volume decreases in pedophiles: only in Amy
R; pedosexual interest and sexual recidivism
associated with GM volume decreases in insular
cortex and DLPFC L, preference for younger
children associated with GM decreases in the
OFC and Ang L/R
Heterosexual (11)
Cantor etal.
MRI White matter
Pedophiles (44)
Teleiophilic sexual
offenders (21)
VBM whole
brain/SPM 2
FDR p<0.05 Reduced WM volumes in pedophiles in Superior
Fronto-Occipital Fasciculus L, Arcuate Fasciculus R
No differences in GM
Offender (53)
Cantor and
MRI White matter
Pedophiles (19) VBM Whole
brain/SPM 2
Not specied p<0.05 Reduced WM volumes in Temporal Lobe L/R
and Parietal Lobe L/R in pedophiles/hebephiles
compared to teleiophiles
Hebephiles (49)
Teleiophiles (47)
Cohen etal.
PET Frontal and
pedophiles (7)
software not
Bonferroni p<0.05 No differences seen in glucose metabolism after
an erotic auditory paradigm; lower metabolism in
ITC and in Superior VFG during neutral auditory
condition in pedophiles compared to controls; no
survival after correction
controls (7)
etal. (2001)
fMRI Orbitofrontal
pedophiles (1)
Visual stimuli
block design/
brain voyager
Not specied Not specied Stronger recruitment in pedophiles in response to
erotic pedohomosexual stimuli: ACC, Brain Stem
R, PFC R, Basal Ganglia R, OFC RControls (2)
Walter etal.
fMRI Hypothalamus
and lateral
prefrontal cortex
Pedophiles (13) Visual stimuli/
Uncorrected p<0.005 Decreased activations in pedophiles to
sexual>emotional arousal contrast: DLPFC R
(Precentral), DLPFC R (MFG/SFG), DLPFC L
(SFG), Occipital Cortex L
Controls (14)
Schiffer etal.
fMRI Frontal and
pedophiles (11)
Visual stimuli/
Whole brain
false discovery
Stronger Activations in pedophiles compared
to controls in contrast nude children/
adults>dressed children/adults: Fus L/R, HC
L/R, Tha R
controls (10)
Schiffer etal.
fMRI Amygdala
pedophiles (8)
Visual sexual
Whole brain
Activations seen in pedophiles compared
to controls in contrast nude children/
adults>dressed children/adults: MFG R,
controls (12)
etal. (2008)
fMRI Amygdala
pedophiles (10)
Visual stimuli/
Uncorrected p<0.005 Activation in pedophiles to children (Boys/
girls)<neutral geometric stimuli contrasts in
Amy R Heterosexual
controls (10)
Poeppl etal.
fMRI Cortical and
Heterosexual (2)
and homosexual (7)
Visual sexual
Whole brain
Activations in pedophiles compared to controls
in contrast nude children>scrambled images of
children: MFG R, Ins L/R, MTG R, IPL L, Pos R,
MCC R, PCC R, HC R, Tha L, Cer RHeterosexual
non-sexual offender
controls (11)
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Method Structural/
PPT groups (n) Paradigm/
Correction Threshold/
etal. (2012)
fMRI Pattern
Heterosexual (11)
and homosexual
(13) pedophiles
Heterosexual (18)
and homosexual
(14) controls
Visual stimuli;
Uncorrected p<0.001/
Deactivations in homosexual pedophiles
compared to controls in boys<men contrast:
Cer L/R, Lin L/R, Anterior Tha L, HC R, Occ L,
Fus L, ITG R, Ang R
Deactivations in heterosexual pedophiles
compared to controls in girls<women contrast:
NC L/R, SPG L/R, ITG L/R, Fus L/R, Cin L, Occ
L, Amy L, Ins L, IFG R, Tha L, Cer R
fMRI Function Heterosexual
pedophiles (8)
Erotic sexual
voyager 2.3.0
Activations in pedophiles in sex×age×group
voxel-wise ANOVA analysis in MiFG R
controls (8)
Kärgel etal.
rsfMRI Function Pedophiles+
CSA (12)
CSA (14)
Healthy Controls
SPM8 and
rsfMRI toolkit
at voxel level;
Family wise
error corrected
at cluster level
DMN: (P-CSA>P+CSA) Diminished
connectivity to left MSF, left OFC. No differences
in opposite contrast (P+CSA>P-CSA).
(HC>P+CSA): VM PFC, OFC. No differences in
P+CSA>HC contrast
Limbic Network: (P-CSA>P+CSA) diminished
connectivity between L Amy and VM PFC,
ACC, OFC, anterior PFC. No differences in
P+CSA>P-CSA. In HC>P+CSA contrast:
increased connectivity between L Amy and L
anterior/inferior PFC, L Lin. No differences in
P+CSA>HC contrast
Poeppl etal.
rsfMRI Function Heterosexual (2)
and homosexual (7)
(MACM) and
FEW at cluster
p<0.05 Seed area: R Amy connected to HC, R ventral
striatum, R Tha, L Amy, L Cla, L hyp, L Put, L HC,
L Mid, L Tha for psychosexual arousal
Heterosexual (11)
L DLPFC: L Ant Ins, DMPFC, L Per, L SPL,
L VLPFC for cognition and perception, spec.
working memory
L Ins: L PaO, L Ant Ins, L Pos, L STG, L Put, R
PaO, R STG, R DLPFC/Ant Ins, R Put, R pMC, L
Tha, R Tha, L Ext for perception and cognition
ACC, anterior cingulate cortex; Amy, amygdala, Ang, angular gyrus, Cau, caudate, CC, corpus callosum; Cer, cerebellum; Cin, cingulate gyrus; Cla, claustrum; DLPFC, dorsolateral
prefrontal cortex; Ext, extrastriate cortex; FPPFC, frontopolar prefrontal cortex (Brodmann area 10); Fus, fusiform gyrus; HC, hippocampus; Hyp, hypothalamus; IFG, inferior
frontal gyrus; Ins, insula; IPL, inferior parietal lobule; ITC, inferior temporal cortex; ITG, inferior temporal gyrus; L/R, left/right; Lin, lingual gyrus; MCC, middle cingulate cortex; MFG,
medial frontal gyrus; MSF, medial superior frontal; Mid, midbrain; MiFG, middle frontal gyrus; MOG, middle occipital gyrus; MTG, middle temporal gyrus; NC, nucleus caudatus;
Occ, occipital lobe; OFC, orbitofrontal cortex; PaO, parietal operculum; Par, paracentral lobule; PCC, posterior cingulate cortex; Pcu, precuneus; Per, peristriate cortex; PHc,
parahippocampal gyrus; Pos, post central gyrus; Pre, precentral gyrus; PSS, posterior cingulate cortex; Put, putamen; SFG, superior frontal gyrus; SI, substantia innominata; SPG,
superior parietal gyrus; SPL, superior parietal lobule; SOG, superior occipital gyrus; STG, superior temporal gyrus; Tha, thalamus; VFG, ventral frontal gyrus.
TABLE 2 | Continued
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A further publication with two case studies highlights the role
of the temporal cortex in regulating sexual behavior (Mendez
et al., 2000). In the rst case, a 60-year-old man developed
fronto-temporal dementia and presented with increased sexual
drive the molestation of extrafamilial children. e second case
was a 67-year-old man who developed hippocampal sclerosis
that similarly increased his sexual desire. He attempted to molest
extrafamilial children. Both patients sexually abused their own
young children, suggesting a latent predisposition to pedophilic
behaviors existed in these patients prior to disease onset. Both
patients showed hypometabolism of the right temporal lobe as
measured with FDG-PET. Aer treatment with antidepressants
(paroxetine for the former patient and sertraline for the latter),
a decrease in pedophilic behaviors and desires was reported
(Mendez etal., 2000). ese ndings support that dysfunction
in the prefrontal cortex may prompt a latent predisposition to
sexual attraction to children through disinhibition, whereas a
dysfunction in the temporal cortex might elicit this response
through sexual preoccupation (Jordan etal., 2011b). is does
not explain the etiology of pedophilia as a sexual preference but as
an acquired hypersexual behavioral disorder, and furthermore one
that rarely presents in the realm of fronto-temporal dementia and
hippocampal sclerosis. Clear here is the expression of pedophilic
behaviors resulting from the neurological diagnoses, but not why
these behaviors were pedophilic rather than hypersexual in nature.
For further discussion of dementia and its relation to hypersexual/
pedophilic disorders, please refer to Mohnke etal. (2014).
Only a handful of studies of MRI-based structural dierences
in pedophilia have been published so far. By means of voxel-based
morphometry (VBM), several alterations of gray matter (GM)
and white matter (WM) were found. In 18 incarcerated exclusive
heterosexual and homosexual pedophilic men with histories of
sexual oending against prepubertal children, a signicantly lower
GM volume in the bilateral orbitofrontal cortex, bilateral insula,
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bilateral ventral striatum (putamen), precuneus, le posterior
cingulate, as well as superior and right middle temporal, parahip-
pocampal gyrus, and in the cingulate compared to 24 teleiophiles
was found. ese ndings were corrected for multiple comparisons
using the false discovery rate within the whole brain (Schier
etal., 2007). However, only the le parahippocampal gyrus would
have remained signicant had a Bonferroni correction for the 15
additional ROI analyses been applied. e authors proposed a
theoretical frontal-executive dysfunction and suggested that –
similarly to obsessive-compulsive spectrum disorders – these
ndings may form a neurophysiological circuit contributing to
the pathophysiology of pedophilia.
In another study with 15 pedophilic forensic inpatients in
comparison to a healthy teleiophile group, GM reductions were
found in four pre-dened ROIs comprised of right amygdalae;
in right septal region, the bed nucleus striae terminalis (BNST),
hypothalamus, and the substantia innominate bilaterally (Schiltz
etal., 2007). Later on, amygdalar volume reduction was conrmed
by a posthoc manual volumetric analysis, unpublished until now
(Schiltz, personal communication). ese results could be related
to a developmental hypoplasia and underscores the inuence of
right amygdalar lateralization on regulation of sexual behavior,
supporting the temporal lobe hypothesis of pedophilia.
One study was published showing that, in comparison to non-
sexual oender controls (n=11), convicted pedophilic oenders
(n=9) show only GM volume decreases in the centromedial nuclei
group of the right amygdala which extended into the lateroba-
sal nuclei group and the cornu ammonis of the hippocampus,
although this nding did not survive correction for the large
number of predened ROIs (Poeppl etal., 2013). Interestingly,
pedosexual interest, including the strength of such interest, and
sexual recidivism were associated with GM volume decreases in the
le insular and dorsolateral prefrontal cortices, while preference
for younger children was associated with GM decreases in the
orbitofrontal cortex and bilateral angular gyri (Poeppl etal., 2013).
What the studies of Schier etal. (2007) and S chiltz etal. (2007)
have in common is a comparison between a group of sentenced sex
oenders recruited from forensic institutions with healthy teleio-
philes without criminal histories, leading to potential confounds in
the results with factors other than pedophilia, such as criminality
or stress of imprisonment. However, an advantage of the study
by Schier etal. (2007) is that they included only pedophiles of
the exclusive type, allowing for interpretations including sexual
By comparing 44 pedophilic men with histories of sexually
oending against children or child pornography consumption,
with 53 men with histories of non-sexual oenses, dierences were
found in the WM only, highlighting a bilateral connection route
traveling the superior fronto-occipital fasciculus, as well as a right-
sided alteration in the arcuate fasciculus. No dierences in GM
were observed (Cantor etal., 2008). ese ndings were upheld
in a follow-up conrmatory reanalysis (Cantor and Blanchard,
2012) and interpreted as insucient connectivity in pedophilic
individuals, rather than simply GM reductions in disparate (sub-)
cortical regions (Cantor and Blanchard, 2012).
Studies to date contain shortcomings either due to the sample
sizes, to the conguration of the control group, or because the
methodology of VBM was used in a restricted way by focusing on
apriori regions of interest. e take home message of the present
structural imaging MRI studies of pedophilia is that while there
have been dierent results from dierent studies, one nding has
been replicated across studies: reduced right amygdala volumes in
pedophiles compared to teleiophilic controls (Mendez etal., 2000;
Schier etal., 2007; Schiltz etal., 2007; Poeppl etal., 2013). is
nding supports the temporal lobe theory of pedophilia referred to
in Section “Introduction and Conceptual Framework.” Diusion-
tensor imaging is a method of WM imaging that holds promise to
validate and expand previous VBM results.
Functional Brain Alterations in Pedophilia
Only a few functional imaging studies have been conducted to
investigate possible dierences during the processing of sexual
stimuli in the brains of pedophiles. With only one exception, they
were visual sexual stimulation studies, thereby inducing a strong
visual bias while making this modality the dominant model of
perceptual processing alterations in paraphilias, although sensory
systems oer potential other routes to sexual responsiveness.
However, with the background of recent evidence explaining how
hetero- or homosexual teleiophilic brains process visual sexual
information and regulate the psychosexual and physiosexual
components of sexual arousal [please refer to Safron etal. (2007),
Georgiadis and Kringelbach (2012), Stoléru et al. (2012), and
Poeppl etal. (2014)] for a deeper discussion), it is a reasonable
step toward the understanding of pedophilia to study whether
there are functional dierences in the brain network associated
with sexually arousing visual pictures of children.
Research has highlighted alterations in pedophiles through
positron emission tomography (PET) and functional MRI. For
example, in a PET study of pedophilia, a decreased regional cerebral
metabolic rate for glucose was found in the right inferior temporal
cortex and superior frontal gyrus, without Bonferroni correction.
is rate decreased in the pedophilic group aer presentation of
girl and women cues, whereas it increased in the teleiophilic group
(Cohen etal., 2002). e authors interpreted this as a consistent
brain abnormality underlying decreased glucose metabolism in
the temporal and frontal cortices implicated in cortical regulation
of sexual arousal. e small sample size of seven participants in
each group limits the generalizability and condence with which
the results can be interpreted.
In fMRI research, the rst study that included a single homo-
sexual pedophile found increased activity of the anterior cingulate
gyrus, right prefrontal cortex, and basal ganglia in response to
pictures of minimally clothed boys, regions that comprise the
attentional brain network with the right orbitofrontal cortex
(Dressing etal., 2001).
Decreased activations were seen in the hypothalamus, dorsal
midbrain, dorsolateral prefrontal cortex, and right lateral parietal,
right ventrolateral, and right occipital cortices, as well as in the
le insula in 13 hetero- and homosexual forensic pedophiles
when viewing sexual stimuli as compared to emotional stimuli
as compared to teleiophiles (Walter etal., 2007). Based on these
ndings, it was suggested that the missing sexual interest toward
adults could be explained by impairment in subcortical regions
associated with the autonomic component of sexual arousal, i.e.,
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lack of activation seen in hypothalamus and dorsal midbrain in
pedophilia. Additionally, using a regression analysis approach, the
activation in the le DLPFC was inversely correlated with the score
on the child abuse subscale of the multiphasic sexual inventory
(MSI), indicating also possible alterations of cognitive processing
of sexual stimuli in these subjects (Schier etal., 2008a,b).
Homosexual and heterosexual incarcerated pedophiles were
examined with fMRI to determine whether there were dier-
ences associated with age and child gender preference. Among
homosexual pedophiles with a history of sexual oenses against
children (n=11) in comparison with homosexual (n=12) con-
trols, the substantia nigra, caudate nucleus, the occipitotemporal
and prefrontal cortices, thalamus, globus pallidus, and the striatum
were activated in response to male child sexual stimuli, whereas
these were not among the matched homosexual teleiophiles
(Schier etal., 2008a). is was interpreted as an increased eort
in evaluating respective stimuli in pedophilic compared to control
participants. In another investigation, heterosexual pedophiles
(n=8), when compared to heterosexual teleiophiles (n=12), aer
presentation with female child sexual stimuli displayed signicant
activations in the amygdala, hippocampus, substantia nigra, cau-
date nucleus, the medial dorsal thalamic nucleus, and the inferior
temporal gyrus, suggesting a similar response pattern to sexually
preferred stimuli as seen in healthy heterosexual males (Schier
etal., 2008b). Pedophilic males showed a signal increase only in
the right dorsolateral prefrontal cortex in response to the preferred
sexual stimuli (no activation was seen in the control group to sexual
stimuli of adult women). An interesting nding was that whereas
the healthy male teleiophiles activated the orbitofrontal cortex in
response to both sexually explicit adult female and female child
imagery, this activation was not seen among male pedophiles. All
together, the authors suggest that orbitofrontal deactivation, as
shown in pedophilic participants, represents a dysfunction of the
neural network necessary for the appropriate cognitive component
of sexual arousal processing.
ere were also attempts to investigate the perception and
emotional processing of visual sexual stimuli. For example, the
right amygdala showed greater activation in homosexual pedo-
philes when they were presented with male child sexual stimuli
compared to heterosexual male teleiophiles who observed female
adult sexual pictures, although the participants were not matched
for sexual orientation, thus potentially obscuring true ‘pedophilic’
activations (Sartorius etal., 2008). e authors interpreted this
increased amygdala activation to stimuli depicting children that
were observed in pedophiles as a possible fearful emotional reac-
tion combined with sexual arousal, supported by the lack of an
appropriate amygdala activation to adult female stimuli (Sartorius
etal., 2008).
Poeppl et al. (2011) used a block design in their study to
investigate sexual interest in pedophiles (nine pedophiles with a
history of contact oenses and 11 non-sexual oender controls)
that consisted of male and female nude Tanner scale imagery,
including Tanner scales I, III, and V, corresponding to prepubes-
cent, pubescent, and adult images. Results of whole brain analyses
showed signicantly greater activation in the middle temporal lobe,
hippocampus, posterior cingulate cortex, thalamus, medial frontal
lobe, and culmen of the cerebellum in pedophiles to the Tanner
I>neutral contrast. When compared to control teleiophiles in
the Tanner V>neutral contrast, pedophiles showed a signicant
deactivation in the right insula. Furthermore, in the between group
contrast of interest (pedophiles>Tanner I, teleiophiles>Tanner
V), there were signicantly greater activation signals seen in the
postcentral gyrus, right middle temporal gyrus, anterior midcingu-
late cortex, and the amygdalae bilaterally (Poeppl etal., 2011). e
authors interpreted these ndings as an easier sexual arousability
in pedophilic as compared to non-paraphilic participants when
stimulated with purposefully non-erotic material (Poeppl etal.,
In a similar study, Habermeyer etal. (2013a) investigated eight
pedophiles (three with a history of contact oenses, ve with a
history of child pornography consumption) and eight heterosexual
teleiophilic controls in an event-related design consisting of erotic
pictures of boys, girls, men, and women. In an ROI analysis includ-
ing the middle frontal gyrus, only the pedophilic participants
showed activation in the girl contrast, whereas controls showed
deactivation (Habermeyer etal., 2013a). A further nding showed
that during the immediate processing of erotic stimuli, both groups
showed signicant activations in the dorsomedial prefrontal cor-
tex, a nding the authors attributed to the crucial role this region
occupies in the critical evaluation of and attention to sexual stimuli
(Habermeyer etal., 2013a).
Two recent studies investigated functional connectivity in
pedophilia and have supported decreased connectivity associated
with CSA, but not with pedophilia. Specically, Kärgel etal. (2015)
examined functional connectivity at rest (RSFC) in 26 pedophilic
men stratied according to oense status (14 P+CSA, 12 P–CSA)
and 14 HC within (1) the default mode network and (2) the limbic
network. Pedophiles who engaged in CSA depicted diminished
RSFC in both networks compared with HC and P–CSA with
diminished RSFC between the le amygdala and orbitofrontal
as well as anterior prefrontal regions. ese ndings highlight
a diminished resting state functional connectivity in oending
pedophiles as compared to controls, suggesting a relationship
to CSA more than to pedophilia. Using complex multimodal
integration of brain structure and function analyses, Poeppl etal.
(2015) found that the functional role of brain regions that are
altered in pedophilia were linked to non-sexual emotional as well
as neurocognitive and executive functions, which were previously
reported to be impaired in pedophiles. ey suggested that struc-
tural brain alterations aect neural networks for sexual processing
by way of disrupted functional connectivity and that structural
alterations also account for common aective and neurocognitive
impairments in pedophilia.
Further, new methods have been investigating dierences that
go beyond regional activations. Pattern classication is a new
method of analyzing neural activation patterns. e idea of pattern
classication is to use activation patterns in dierent brain regions
in a multivariate approach rather than relying on region by region
comparisons (Linden, 2012). It can be used for classifying groups.
For example, in the eld of sexology pattern classication has been
applied successfully to classify heterosexual and homosexual male
teleiophiles (Ponseti etal., 2009).
Research found that the activations seen in heterosexual and
homosexual pedophiles to child stimuli are nearly indistinguishable
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from those in heterosexual and homosexual healthy males to
adult stimuli (Ponseti etal., 2012); this supports the assumption
that pedophilia is primarily a sexual age preference similarly
to teleiophilia. e activation pattern among heterosexual and
homosexual pedophiles and healthy male teleiophiles includes the
caudate nucleus, cingulate cortex, insula, fusiform gyrus, temporal
cortex, occipital cortex, thalamus, amygdala, and cerebellum.
Despite the similarity in activation patterns between pedophilic
and teleiophilic men, the novel pattern classication technique has
been successfully applied based on the presentation of preferred
sexual stimuli and resulted in a mean accuracy of 95%, with 100%
specicity and 88% sensitivity (Ponseti etal., 2012; Mohnke etal.,
2014), thereby showing a promising new approach for classify-
ing subjects. Please refer to Figure3 for a visual explanation of
pattern classication according to Ponseti etal. (2012). ese
studies included fully admitting pedophilic participants only;
therefore, further research should verify its use with partially- or
non-admitting pedophiles. e promise of functional predictors
is, however, also supported by a similar study which, in contrast
to Ponseti etal. (2012), used a highly hypothesis-driven approach
of several impaired functions.
In their study, Walter etal. (2010) could show that a bi-dimen-
sional discriminant function analysis revealed highly signicant
group separation when activations for cognitive appraisal or
passive consumption of visual material are considered in their
respective specic brain regions. A recent study investigated
response inhibition in pedophilic males and found that pedophilic
participants had slower reaction times and less accurate visual
target discrimination which corresponded to greater activation
in the “No-Go” condition for the DLPFC bilaterally, frontal eye
elds, and supplementary motor areas, but in the le anterior cin-
gulate cortex, precuneus, and angular gyrus, they showed greater
activation in the “Go” condition (Habermeyer etal., 2013b) in an
uncorrected voxel-wise analysis.
As research shows, there are regions that dier in neural activa-
tion among heterosexual pedophiles, homosexual pedophiles, and
matched healthy teleiophiles. However, limitations in these early
studies included controlling neither for sexual preference nor
orientation, using insuciently dierentiated inter-study para-
digms such that all generalizations had to be limited to the exact
study and paradigm utilized. Furthermore, pedophilic participants
were all incarcerated or judicially involved [a notable exclusion
to this being (Ponseti etal., 2012)], underscoring the need for
studies investigating non-incarcerated pedophilic participants. As
previous research in normal human sexuality has shown, there are
notable dierences between healthy heterosexual and homosexual
men. is should be kept in mind for future neuroscientic inves-
tigations (Hamann etal., 2004; Ponseti etal., 2006, 2009).
As discussed previously, neuroimaging is a useful way of
investigating the neural correlates of human sexuality in terms of
detecting the arousal pattern associated to the sexual preference
structure. A criticism of previous functional neuroimaging studies
FIGURE 3 | Illustration of pattern classication of pedophiles and healthy controls using individual expression values. Participants with p >0.5
(dark area) were classied as pedophiles. For further details, see Ponseti etal. (2012).
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in pedophilia relates to faking. Under the assumption that immedi-
ate processing of sexual stimuli is outside of conscious cognitive
control (bottom-up inuence), results were interpreted so that
(de)-activations were true and not the result of faking (Ponseti
etal., 2009, 2012, 2014). However, studies of test-retest reliabilities
and faking in fMRI research have shown that faking can and does
occur (Lee etal., 2009) and that, ndings are not always reliable
across centers and studies (Maitra etal., 2002; Raemaekers etal.,
2007; Friedman etal., 2008). With the aforementioned limitations
in mind, new research programs will help to dierentiate the true
dierences from methodological artifacts.
The Contribution of Molecular Genetics and
Even though rst hints for a familial transmission of pedophilia
date back to the early 80s (Ganey etal., 1984), only limited
research has been conducted into the genetic contributions to
pedophilia. Twin studies of sexual orientation hint at a heritable
component of homosexuality (Bailey etal., 2000; Santtila etal.,
2008; Långström et al., 2010). Most recently, a Finnish group
published the rst twin study investigating pedophilia. is was a
population-based twin design analyzing 3967 male twins and their
male siblings. It was shown that genetic inuences contribute to
sexual interest, fantasies, or activity pertaining to children under
the age of 16years (Alanko etal., 2010). However, the heritability
estimated in the study explained only 14.6% of the variance; in
comparison, the heritability of almost all psychiatric disorders
is estimated to be above 30%, with schizophrenia and bipolar
disorder ranging as high as 70–80% (Alanko etal., 2013). Based
on their ndings, the authors concluded that future research
should address the possible interplay of genetic with environ-
mental risk factors, such as own sexual victimization in child-
hood (Bienvenu etal., 2011). Another recently published study
reported genograms of ve families with unusual high occurrence
of paraphilias (mainly pedophilia). ey found familial aggrega-
tion of paraphilias with no clear Mendelian type of transmission.
Intriguingly these families included carriers for dierent types
of possible developmental disorders such as conduct disorders,
deafness, blindness, and epilepsy (Labelle etal., 2012).
No candidate studies nor genome-wide association studies
in the eld of pedophilia have been published today and to our
knowledge, no large-scale eorts to ll this gap are currently under
way. is would also not be feasible considering that the number of
subjects needed in order to expect genome-wide signicant nd-
ings would be in the range of several thousand or ten-thousand.
Given the weak heritability of pedophilia together with the
assumed large eects of early environment and early develop-
ment, and possibly an interaction among these dierent factors,
epigenetics might represent a promising way to disentangle the
biological substrates and possible markers of sexual deviation.
Epigenetics is the study of the dynamic changes in gene regulation,
which the organism achieves using the common mechanisms
of DNA methylation, histone modication, and chromatine
restructuring (Rodenhiser and Mann, 2006). rough epigenetic
mechanisms, the organism can establish a molecular memory of
past gene×environment interactions, with long-lasting eects
on brain circuits and genetic pathways. For example, early life
stress programs the function of the HPA-axis through epigenetic
alterations in the regulation of key genes involved in HPA axis
functioning (Szyf etal., 2005; McGowan etal., 2009; Muragtroyd
etal., 2009). Epigenetic (dys-) regulation plays an important role
in dierent neuropsychiatric disorders and was proven as a suc-
cessful heuristic framework for research in neurodevelopmental
disorders (Krebs etal., 2004; Schroeder etal., 2012). Epigenetic
mechanisms are also involved in the process of tissue dierentia-
tion (Rodenhiser and Mann, 2006) as well as in normal sexual
dimorphic brain development (Nugent etal., 2011). Recent nd-
ings give rise to the view that epigenetic mechanisms are at the
core of sexual dierentiation and serve as the interface between
hormonally transmitted changes and sex chromosome related
eects (Arnold etal., 2012). Its implication in both normal and
abnormal brain development, as well as its role in the etiology
of psychiatric disorders, makes it likely that epigenetic mecha-
nisms widely contribute to the development of the human sexual
preference structure including pedophilia. However, to date, no
investigations of epigenetics in this direction have been published.
Conclusion: What are the Implications and
Future Directions of Neurobiology and
Previous research investigated the etiology of pedophilia from
a neurobiological and neurodevelopmental perspective, utiliz-
ing state-of-the-art neuroimaging equipment and methods and
physical markers known to be highly inuenced by developmental
challenges. Although the idea of a neurodevelopmental etiology of
pedophilia has a very wide scope and this idea can be attributed to
other psychological disorders, we feel its relationship to pedophilia
warrants stricter research.
Support for a neurodevelopmental pathway comes from
research investigating epigenetic dysregulation of sexual develop-
ment in general, physical characteristics, and functional as well
as structural brain dierences in pedophilia. Pedophilia seems
to have a small hereditary component, with cases clustering in
families and familial transmission of deviant sexual fantasies and
behaviors (Ganey etal., 1984; Alanko etal., 2010).
Sexually oending and incarcerated pedophilic men show
increased rates of le-handedness, have shorter stature, experi-
ence twice as many head injuries before the age of 13 as normal
counterparts, and seem to have lower intelligence than teleiophilic
men (Blanchard etal., 2003, 2007; Cantor etal., 2004, 2005, 2007).
ese variables are present in pedophilic men signicantly more
oen than in healthy control, but it is not clear if the reason for
this is the sexual behavior disorder, the pedophilic preference, or
even another factor.
e push for neurobiological research has resulted in three
major aforementioned theoretical developments, all attempting
to explain various aspects of pedophilia. e frontal lobe theory
is a contender to explain oenses against children from behavioral
disinhibition and uncontrolled compulsive behaviors. Noticeable
structural and functional dierences in size and function of the
le and right dorsolateral prefrontal and orbitofrontal cortex have
been found in pedophilic men with a history of contact sexual
June 2015 | Volume 9 | Article 34416
Tenbergen et al. The neurobiology of pedophilia
Frontiers in Human Neuroscience |
•Altered 2D:D4 rao
•Rates of le
Life events
•Stressful events during
childhood including
child sexual abuse
•Number of head
injuries before age of
13 years ↑
•Lower IQ & shorter
sex drive due
to low serotonergic
sex drive due
to high dopaminergic
•Decreased prefrontal
and temporal
•Alteraon of
•Volume reducon of
amygdala and
FIGURE 4 | Findings and questions regarding the etiology of pedophilia.
oenses against children (Burns and Swerdlow, 2003; Schier etal.,
2007, 2008a,b; Poeppl etal., 2011).
e temporal-limbic theory tries to explain pedophilia through
structural and functional dierences in the temporal lobes, thus
focusing on the misattributed emotional salience and valence
toward children. Several case studies highlight temporal and
amygdalar lesions or functional activation dierences that might
contribute to the development of a pedophilic sexual preference
(Cohen etal., 2002; Joyal etal., 2007; Schiltz etal., 2007; Walter
etal., 2007; Sartorius etal., 2008).
e dual lobe theory suggests that both frontal and temporal
disturbances are responsible for the range of behaviors seen in
pedophilia, such as diminished impulse control as seen with
orbitofrontal decits and hypersexuality through the temporal
lobes (Seto, 2008, 2009; Poeppl etal., 2013).
erefore, future investigations in the neuroimaging of pedo-
philia should use stricter inclusion/exclusion criteria to better
limit potential confounds and actively recruit non-oending
pedophiles to close the gap in knowledge between oending
and non-oending pedophiles. is will also aid in researchers’
abilities to understand exactly what regions of the brain are
implicated in pedophilic sexual preference development, as
current literature interpretation implicates the brain in an overly
ambitious manner. Examinations of the symptomatology and
clinical aspects of pedophilia should rst try to replicate original
ndings before novel ideas can be properly tested, including
testosterone and its role in pedophilia development or the role
of neurotransmitters such as dopamine and serotonin and their
receptor densities in relation to behavioral perturbations. What
is ultimately needed in this research eld are stricter participant
inclusion criteria and studies utilizing non-oending pedophiles
and non-pedophilic oenders in order to ascertain what dier-
ences are true to pedophilia and those that are true to sexual
oending against children in general. Please refer to Figure4
for a visual of research questions and directions for the etiology
and treatment of pedophilia.
Now that pedophilia is an increasingly accepted research
eld and not only a side issue, scientists are more intensively
investigating not only how it develops, but also how to treat, and
ultimately, how to prevent oending against children. Ultimately,
the success rests with researchers willing to investigate a topic
that still carries a signicant societal stigma load but promises
to oer a signicant improvement not only to patients but also
to society in general.
June 2015 | Volume 9 | Article 34417
Tenbergen et al. The neurobiology of pedophilia
Frontiers in Human Neuroscience |
We would like the thank Mr. Alexander Pohl and Mr. Sebastian
Mohnke for their insightful comments and expertise during revi-
sion, as well as the reviewers’ comments that helped improve our
manuscript. Support for this manuscript was provided by a grant
from the German Ministry for Education and Research (BMBF)
awarded to JP, MW, KB, BS, and TK (01KR1205A), and a grant
from the German Research Foundation (DFG) awarded to BS and
TK (Schi 1034/3-1). e funding sources played no further role in
the manuscript design or preparation or in the decision to submit
the manuscript for publication.
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Conict of Interest Statement:e authors declare that the research was conducted
in the absence of any commercial or nancial relationships that could be construed
as a potential conict of interest. e Reviewer Stuart Brody declares that, despite
having collaborated with the author Tillmann H. C. Kruger, the review process was
handled objectively.
Copyright © 2015 Tenbergen, Wittfoth, Frieling, Ponseti, Walter, Walter, Beier, Schier
and Kruger. is is an open-access article distributed under the terms of the Creative
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... So far, structural neuroimaging studies were unable to robustly identify gray matter volume (GMV) patterns associated with the diagnosis of pedophilia (19). The GMV patterns found in previous neuroimaging studies, specifically in orbitofrontal, limbic, and basal ganglia structures, turned out to be much more closely associated with PO individuals than with pedophilia alone (19)(20)(21)(22)(23). Consequently, diffusion-tensor imaging (DTI) studies reported an increase in fractional anisotropy (FA) in the white matter of the left hemisphere (24) and FA reductions in the corpus callosum (23) in PO individuals compared to healthy control subjects and nonoffending pedophilic individuals. ...
... Therefore, it has been suggested that PO individuals could have the most distinct neurobiological footprint of all these groups (10). Due to their commission of pedosexual crimes, the PO subpopulation is also forensically the most relevant subpopulation (10,20,21). ...
... We present an exploratory proof-of-principle study that uses supervised machine learning and structural magnetic resonance imaging to derive a neuroanatomical model for PO individuals and evaluate its clinical utility in diagnosis and risk assessment. In a sample of 14 PO and 15 healthy control (HC) individuals, we analyzed DTI data from a literature-based selection of brain regions (prefrontal cortex, anterior cingulate cortex, amygdala, and corpus callosum) (20,21), trained a support vector machine on these MRI features to distinguish between PO and HC individuals and applied the final PO model to an external sample of 53 HC individuals for further evaluation of model specificity. In addition, we used stepwise linear regression to investigate the clinical and forensic implications of the PO model with respect to measures of psychopathy, delinquency, sexual deviance, and sociodemographic characteristics. ...
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Background Child sexual abuse (CSA) has become a focal point for lawmakers, law enforcement, and mental health professionals. With high prevalence rates around the world and far-reaching, often chronic, individual, and societal implications, CSA and its leading risk factor, pedophilia, have been well investigated. This has led to a wide range of clinical tools and actuarial instruments for diagnosis and risk assessment regarding CSA. However, the neurobiological underpinnings of pedosexual behavior, specifically regarding hands-on pedophilic offenders (PO), remain elusive. Such biomarkers for PO individuals could potentially improve the early detection of high-risk PO individuals and enhance efforts to prevent future CSA. Aim To use machine learning and MRI data to identify PO individuals. Methods From a single-center male cohort of 14 PO individuals and 15 matched healthy control (HC) individuals, we acquired diffusion tensor imaging data (anisotropy, diffusivity, and fiber tracking) in literature-based regions of interest (prefrontal cortex, anterior cingulate cortex, amygdala, and corpus callosum). We trained a linear support vector machine to discriminate between PO and HC individuals using these WM microstructure data. Post hoc , we investigated the PO model decision scores with respect to sociodemographic (age, education, and IQ) and forensic characteristics (psychopathy, sexual deviance, and future risk of sexual violence) in the PO subpopulation. We assessed model specificity in an external cohort of 53 HC individuals. Results The classifier discriminated PO from HC individuals with a balanced accuracy of 75.5% (sensitivity = 64.3%, specificity = 86.7%, P 5000 = 0.018) and an out-of-sample specificity to correctly identify HC individuals of 94.3%. The predictive brain pattern contained bilateral fractional anisotropy in the anterior cingulate cortex, diffusivity in the left amygdala, and structural prefrontal cortex-amygdala connectivity in both hemispheres. This brain pattern was associated with the number of previous child victims, the current stance on sexuality, and the professionally assessed risk of future sexual violent reoffending. Conclusion Aberrant white matter microstructure in the prefronto-temporo-limbic circuit could be a potential neurobiological correlate for PO individuals at high-risk of reoffending with CSA. Although preliminary and exploratory at this point, our findings highlight the general potential of MRI-based biomarkers and particularly WM microstructure patterns for future CSA risk assessment and preventive efforts.
... Therefore, their etiology differs significantly. The etiology of developmental pedophilia is still unknown, but it is thought to be multifactorial [42][43][44], with genetics, stressful life events, testosterone exposure, neurochemical impairment and comorbidity with psychopathology all playing a pivotal role; this is in contrast to the etiology of acquired pedophilia, which is known and depends on the underlying neurological disorder. For instance, if the underlying neurological disorder is a brain tumor, then the etiology is neoplastic, while if the underlying condition is frontotemporal dementia, then the etiology is degenerative. ...
... In other words, the brain regions in which the synergic functioning is abnormal in the two forms of pedophilia are unknown. Regarding idiopathic pedophilia, some studies have attempted to shed light on structural or functional alterations [42,[47][48][49][50][51][52][53][54][55], but a recent meta-analysis concluded that the results do not spatially converge across different studies [10]; in other words, different studies have reported different results. Thus, to date, there are no consistent subtle brain alterations associated with developmental pedophilia. ...
... It is thus of the utmost importance to clarify the behavioral and clinical characterization of acquired pedophiles to help clinicians clarify which behavioral red flags could raise the suspicion of an acquired origin of pedophilia. Furthermore, it would also be helpful to shed light on both the neural network potentially involved in the two different forms of pedophilia-which is a topic that has thus far remained underexplored [10,42,48]-and the neuroscientific methodologies that could be considered important for the differential diagnosis between acquired and developmental pedophilia. Finally, the levels of awareness between the scientific and nonscientific communities should be raised with regard to the consequences of misdiagnosis, and critically, a consensus within the scientific community should be achieved with regard to the legal implications of such a disease. ...
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Idiopathic and acquired pedophilia are two different disorders with two different etiologies. However, the differential diagnosis is still very difficult, as the behavioral indicators used to discriminate the two forms of pedophilia are underexplored, and clinicians are still devoid of clear guidelines describing the clinical and neuroscientific investigations suggested to help them with this difficult task. Furthermore, the consequences of misdiagnosis are not known, and a consensus regarding the legal consequences for the two kinds of offenders is still lacking. The present study used the Delphi method to reach a global consensus on the following six topics: behavioral indicators/red flags helpful for differential diagnosis; neurological conditions potentially leading to acquired pedophilia; neuroscientific investigations important for a correct understanding of the case; consequences of misdiagnosis; legal consequences; and issues and future perspectives. An international and multidisciplinary board of scientists and clinicians took part in the consensus statements as Delphi members. The Delphi panel comprised 52 raters with interdisciplinary competencies, including neurologists, psychiatrists, neuropsychologists, forensic psychologists, expert in ethics, etc. The final recommendations consisted of 63 statements covering the six different topics. The current study is the first expert consensus on a delicate topic such as pedophilia. Important exploitable consensual recommendations that can ultimately be of immediate use by clinicians to help with differential diagnosis and plan and guide therapeutic interventions are described, as well as future perspectives for researchers.
... "Pedophilia does not always occur in isolation, because men with this disorder often have a significant history of psychiatric disorders, which in extreme cases can overshadow the discovery of etiology. Whether it is a secondary phenomenon related to this tendency's emotional and social consequences or whether these are true comorbidities is still difficult to prove" (Tenbergen et al., 2015). So, from a clinical point of view, there are people with pedophilic disorder who limit their obsession with sexual contact with children exclusively to fantasy, as opposed to the category of pedophiles whose behavior inevitably leads to the commission of a criminal act, due to the inability to refrain, that is, the inability to achieve self-control. ...
... Following the patterns of behavior, the third category of perpetrators of crimes against children, who were not the initial product of pedophilia, is also recognized. "These are surrogate types of sexual offenders, and they can be diagnosed with a condition in the category of impulse control disorder, which represents a lack of sexual inclination towards children, but the act of Child Sexual Abuse has been committed" (Tenbergen et al., 2015). ...
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Paraphilias represent a group of disorders characterized by a pathological sexual tendency or anomaly, with the impulses including intense sexual fantasies and urges that keep returning in regard to the unusual objects, activities, circumstances, and/or certain category such as the children. Pedophilia belongs to this group of disorders and it is alternatively labeled as a pedophile disorder, which includes specific incriminated actions, which in addition to prison sentences, generally result in a social stigmatization of not only perpetrators but victims too. It is a sexual affinity disorder mostly found in adults who have expressed sexual fantasies and a tendency to enter the sexual relations with children of the same or the opposite sex. Nowadays, a “digital space” has become a unique environment where these specific crimes take place, and the border between the virtual and real world is practically indistinguishable. In this digital environment, pedophiles and other sexual predators have got a new space in which they establish spontaneous contacts with potential victims (often with children). In a manipulative way, they recruit vulnerable individuals with the aim of various forms of abuse and sexual exploitation. Considering the fact that it is a delicate and variable disorder, which calls for an interdisciplinary approach, profiling these persons is crucial in relation to any countermeasure. Profiling is also necessary to systematically investigate the symptoms, nature, and factors of psychopathological conditions and deviations in the existences of the affected persons. After all, it is one of the ways of reaction to make pedophilia more visible as a part of preventive programs before the late manifestation. In this paper, there are applied the methods of a quantitative and qualitative content analysis, comparative analysis (reaction to pedophilia) as well as a descriptive and analytical statistics. The purposeful goal is to recognize pedophilia as a sociopathological phenomenon that requires an adequate response from the social community.
... Los avances actuales de las neurociencias han permitido identificar alteraciones en áreas cerebrales que desempeñan un importante rol en los aspectos cognitivos del deseo sexual y la inhibición conductual, en las cuales se identifica que existe un efecto negativo a partir de los eventos adversos que puede suceder durante el desarrollo prenatal o la primera infancia; esto señala que se trata de un fenómeno complejo y multifactorial donde influye la genética, los eventos estresantes de la vida, los procesos específicos de aprendizaje, así como las perturbaciones en la integridad estructural del cerebro de una persona con el trastorno; esto podría generar un fenotipo específico de preferencia sexual. Según Tenbergen et al. (2015), las primeras teorías que trataban de explicar el origen de este deseo sexual iniciaban estableciendo que el niño que era abusado sexualmente, en la etapa adulta sería un abusador infantil también. Sin embargo, los nuevos hallazgos biológicos proponen diversos factores que podrían estar involucrados en el origen de la pedofilia, como las activaciones de la corteza prefrontal y orbitofrontal, encargadas de inhibir distintos impulsos incluyendo el sexual, lo que explicaría cómo ciertas estructuras cerebrales como el lóbulo temporal pueden estar vinculados con la hipersexualidad. ...
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This article shows a case intervention in a patient diagnosed with sexual preference disorder through post-rationalist cognitive therapy. The article delivers an identification of the concepts of Organizations of Personal Meaning, identity types and personality styles; fragments of the session are used to carry out discourse analysis, showing the problematic foci in the patient and the process of change observed throughout the therapeutic process. Intervention was carried out in 22 treatment sessions and the main techniques were the Moviola technique, autobiography and Socratic dialogue. These narrative techniques were fundamental to facilitate in the establishment of a more coherent sense of self, assuming and accepting his homosexual orientation, resulting in a notorious decrease in the frequency and discomfort associated with pedophilic thoughts.
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This is a copy of the workshop presentation I gave for the Association for Sexual Abuse Prevention on February 25th, 2023.