Oxytocin receptor (OXTR) and serotonin
transporter (5-HTT) genes associated with
Marian J. Bakermans-Kranenburg and Marinus H. van IJzendoorn
Centre for Child and Family Studies, Leiden University, The Netherlands
Both oxytocin and serotonin modulate affiliative responses to partners and offspring. Animal studies suggest a crucial role of
oxytocin in mammalian parturition and lactation but also in parenting and social interactions with offspring. The serotonergic
system may also be important through its influence on mood and the release of oxytocin. We examined the role of serotonin
transporter (5-HTT) and oxytocin receptor (OXTR) genes in explaining differences in sensitive parenting in a community sample of
159 Caucasian, middle-class mothers with their 2-year-old toddlers at risk for externalizing behavior problems, taking into
account maternal educational level, maternal depression and the quality of the marital relationship. Independent genetic effects
of 5-HTTLPR SCL6A4 and OXTR rs53576 on observed maternal sensitivity were found. Controlling for differences in maternal
education, depression and marital discord, parents with the possibly less efficient variants of the serotonergic (5-HTT ss) and
oxytonergic (AA/AG) system genes showed lower levels of sensitive responsiveness to their toddlers. Two-way and three-way
interactions with marital discord or depression were not significant. This first study on the role of both OXTR and 5-HTT genes in
human parenting points to molecular genetic differences that may be implicated in the production of oxytocin explaining
differences in sensitive parenting.
Keywords: parenting; sensitivity; oxytocin receptor (OXTR) gene; serotonin transporter (5-HTT) gene; marital discord; maternal
Although the development of offspring is shaped by their
genetics, parenting also plays a central role in determining
the individual child’s adaptation to the social environment
in various non-human species (Suomi, 1999; Meaney, 2001;
Meaney and Szyf, 2005), as well as in humans (Cummings
and Davies, 2002; Repetti et al., 2002; Sroufe et al., 2005). In
particular parental sensitivity, defined as the ability to
accurately perceive children’s signals and to respond in an
adequate and prompt way (Ainsworth et al., 1978) has been
documented to be crucial in the development of the
offspring’s capacity to establish attachments to protective
adults and to regulate stress (Bowlby, 1969/1982; Cassidy
and Shaver, 1999; Bakermans-Kranenburg et al., 2003).
Almost no molecular genetic studies of parenting in
humans have been conducted (Swain et al., 2007). In a
previous report on the current sample we focused on two
dopamine-related genes (Dopamine D4 Receptor, DRD4 and
Catechol-O-Methyltransferase, COMT), showing that daily
hassles were strongly associated with less sensitive parenting
in parents with the combination of genes leading to less
efficient dopaminergic system functioning, whereas the most
efficient combination (COMT met/met, no DRD4-7 Repeat)
appeared to buffer the negative effect of daily hassles on
maternal sensitivity (Van IJzendoorn et al., 2007). In the
current report we examine the role of oxytocin receptor
(OXTR) and serotonin transporter (5-HTT) genes in
explaining differences in sensitive parenting, taking into
account maternal depression and the quality of the marital
relationship. Marital relationships belong to the most crucial
affiliative social systems with great import for the way in
which mothers care for their children (Belsky, 1984;
Cummings and Davies, 2002; Repetti et al., 2002).
Carter (1998) in her seminal ‘Neuroendocrine perspec-
tives on social attachments and love’ proposed a crucial role
of oxytocin not only in mammalian parturition and lactation
but also in parenting, by reducing neophobia and feelings
of stress and enhancing the reward value of social
interactions with the offspring. The important role of
oxytocin in parental behavior of rodents (Lim and Young,
2006; Olaza ´bal and Young, 2006) and sheep (Keverne and
Kendrick, 1992) has been documented extensively. Similar
data for non-human primates and humans are almost absent
Received 16 November 2007; Accepted 21 January 2008
Advance Access publication 11 February 2008
This study is a part of the research project ‘Screening and Intervention of Problem behavior in Toddlerhood’
(SCRIPT), conducted at the Centre for Child and Family Studies, Leiden University, The Netherlands. The study is
supported by grant 2200.0097 from ZonMw (Netherlands Organization for Health Research and Development)
to Marinus H. van IJzendoorn and Femmie Juffer. Support from The Netherlands Organization for Scientific
Research NWO (VIDI, SPINOZA Prize) to M.J. Bakermans-Kranenburg and Marinus H. van IJzendoorn,
respectively, is also gratefully acknowledged. We thank Dr Jantien van Zeijl, Dr Mirjam Stolk, Dr Lenneke Alink,
Dr Judi Mesman, Dr Femke Pijlman, Prof Femmie Juffer and Prof Hans Koot for their contributions to the various
parts of the study and Base-Clear for the genotyping. Last but not least we thank the parents and children who
participated in our study, as well as the students who assisted in various phases of the SCRIPT project.
The contributions of the first and the second author to this paper are equal.
Correspondence should be addressed to Prof. Marian J. Bakermans-Kranenburg, Centre for Child
and Family Studies, Leiden University, PO Box 9555, NL-2300 RB Leiden, The Netherlands.
doi:10.1093/scan/nsn004SCAN (2008) 3,128–134
? The Author(2008).PublishedbyOxfordUniversityPress.For Permissions,pleaseemail:email@example.com
(Maestripieri, 1999; Numan and Insel, 2003), although
recently oxytocin levels in human mothers were found to be
related to parenting in the first month after birth (Feldman
et al., 2007).
Circumstantial evidence for the potentially important role
of oxytocin in human parenting may be derived from
experimental studies administering oxytocin to patients
with autism, which enhanced their social cognitions and
empathic feelings (Bartz and Hollander, 2006), and in
studies relating autism to variations in the oxytocin receptor
gene (Wu et al., 2005; Ylisaukko-oja et al., 2006; Jacob et al.,
2007). In a study with non-clinical individuals, intranasal
oxytocin administration increased feelings of interpersonal
trust (Kosfeld et al., 2005). In a non-clinical adult female
sample Tops et al. (2007) found plasma oxytocin levels to
be strongly associated with attachment defined as the
tendency to express and share emotions and feelings with
partners or close friends. These findings appear to support
Carter’s (1998) suggestion that oxytocin is important for
intimate attachments such as marital relationships and
interactions with offspring.
The serotonergic system may be important in this regard
through its association with depression (particularly in the
face of stressful life events, see for a review Uher and
McGuffin, 2008) but also through its potential influence on
the release of oxytocin. Serotonergic fibers have preferential
input to oxytonergic regions in macaques and other animals,
and both oxytocin and serotonin can modulate affiliative
responses to partners and offspring (Emiliano et al., 2007).
Stimulation of the hypothalamus by serotonin has been
shown to lead to release of oxytocin as a precursor molecule
(Lee et al., 2003). Galfi et al. (2005) found that in rats
oxytocin secretion was influenced directly by the serotoner-
gic system (Jorgensen et al., 2003). Although the serotonergic
system has been implicated in anxiety, affiliation and reward,
little evidence for its role in parental behavior is available
(Numan and Insel, 2003; D’Souza and Craik, 2006). The
serotonergic system may however be important for respond-
ing sensitively to the partner as well as to the offspring, partly
through its influence on the release of oxytocin.
In the current investigation we examine the associations
between 5-HTT and OXTR genes and parenting, focusing on
one of the variants of each gene (5-HTTLPR SCL6A4 and
OXTR rs53576). We expect to find lower levels of parental
sensitive responsiveness in parents who as a result of their
serotonergic and oxytonergic system genes are supposed
to have less efficient oxytocin production. We test whether
this association is dependent on the quality of the marital
relationship and we control for differences in maternal
educational level and depression. Finally we examine
whether the effect sizes related to the genetic differences
are comparable to those implicated in the environmental
The current article is based on data obtained in the SCRIPT
study (Screening and Intervention of Problem behavior in
Toddlerhood), which investigated the effectiveness of an
early intervention program aimed at reducing externalizing
problems in 1–3-year-old children by enhancing maternal
sensitivity and adequate discipline strategies (Van Zeijl et al.,
2006). It consisted of a screening phase in a general
population sample and a pretest-posttest randomized case-
control intervention in a subsample of children (n¼237)
with scores above the 75th percentile on the CBCL
Externalizing Problems scale (Achenbach and Rescorla,
2000). Mother and child completed several tasks (e.g. free
play, puzzles, see Van Zeijl et al., 2006) during a 1.5h
(pretest) laboratory session. About 3 years after this pretest
session the participants were contacted to take part in the
collection of DNA material. Cheek cells were collected from
176 mothers. These mothers (mean age 33 years, s.d.¼4.1)
did not significantly differ from mothers who did not
participate in the genetic part of the study on age, sensitivity,
marital discord, depression, child age or gender and number
of children. They were however slightly better educated
(M¼3.66, s.d.¼1.06 on a scale ranging from 1¼ elemen-
tary school to 5¼at least BA degree) than non-participating
mothers (M¼3.33, s.d.¼1.08). Fifty-seven percent of the
children were boys. Since data for the current article were
derived from the screening and pretest phases the interven-
tion and control groups were combined in the analyses.
Permission for the study was obtained from the Committee
for Medical Ethics of Leiden University Medical Centre and
the Ethics Committee of the Faculty of Social and Behavioral
Sciences of Leiden University.
dlers was observed in the laboratory session during a series of
problem-solving tasks. Dyads were given three tasks during a
total time of 15min; they were asked to solve puzzles that
were too difficult for the child, and mothers were instructed
to help their child in the way they usually did. Mothers’
supportive presence, intrusiveness and clarity of instruction
were rated on 7-point scales drawn from Egeland et al.
(1990). These scales include and extend Ainsworth et al. ’s
(1978) original scales for ‘sensitive responsiveness’ developed
for parent–infant interaction in the first year after birth.
The Egeland et al. (1990) observational scales take the wider
age range of the current sample into account and measure
an age-appropriate concept of sensitivity that also pertains
to the developmental domain of coping with cognitive
challenges. The average intraclass correlation (single rater,
absolute agreement) for intercoder reliability (for all separate
pairs of seven coders) was .75 (n¼30). For the overall
sensitivity score, ratings of the separate tasks were averaged,
Mothers’ sensitive interaction with their tod-
Oxytocin andserotoningenes andparenting SCAN (2008)129
the intrusiveness scores were reversed and the standardized
subscale scores were added.
Marital discord was assessed using a
subscale of the Dutch Family Problems Questionnaire (Koot,
1997). The mothers indicated on a 3-point scale whether five
statements about their partner relationship and partner
support were 0 not true, 1 somewhat or sometimes true, or 2
true or often true. Reliability and validity of this scale were
demonstrated by Koot (1997); the internal consistency
(Cronbach’s alpha) in our sample was 0.66. A total score
was computed by summing item scores.
Mothers completed the short
form of the Young Adult Self-Report (YASR, Achenbach,
1997). We used a short form, consisting of the 29 items that
were found to discriminate best between referred and non-
referred samples (Achenbach, 1997). The internal consis-
tency (Cronbach’s alpha) in our sample was 0.89. A total
score was computed by summing item scores.
Buccal swabs from the mothers were
collected in lysis buffer (100mM NaCl, 10mM EDTA,
10mM Tris pH 8, 0.1mg/ml proteinase K and 0.5% w/v
SDS) until further processing. Genomic DNA was isolated
from the samples using the Chemagic buccal swab kit on a
Chemagen Module I workstation (Chemagen Biopolymer-
Technologie AG, Baesweiler, Germany). DNA concentra-
tions were measured using the Quant-iT DNA Assay kit
(Invitrogen, Breda, The Netherlands). The average yield was
4mg of genomic DNA per buccal swab sample.
The 5-HTTLPR polymorphism in the promoter region of
the SLC6A4 gene was genotyped by PCR amplification
followed by agarose gel electrophoresis. The forward primer
reverse primer was 50-GGACCGCAAGGTGGGCGGGA-30
(Gelernter et al., 1997). These primers produce a short
fragment of 375bp representing the 14 repeat allele (‘s’) and
a long fragment of 419bp representing the 16 repeat allele
(‘l’). PCR fragments containing the 5-HTTLPR polymorph-
ism were obtained in a total reaction volume of 25ml,
containing 50ng of genomic DNA, 0.3mM dNTPs, 1.5mM
MgCl2þ, 10pmol of each primer and 0.3U of BioThermAB
polymerase (Genecraft, Munster, Germany). PCR conditions
were the following: an initial denaturation step of 10min at
948C, 36 cycles of 30s at 948C, 1min at 688C and 1min at
728C, followed by a final extension step of 15min at 728C.
The amplification products were separated on a 2% agarose
gel with 0.001% ethidium bromide and visualized by
ultraviolet transillumination. Difficult cases were re-geno-
typed two more times. Genotyping was unambiguous in 159
cases. Genotypes (n¼38 ss, n¼65 sl, n¼56 ll) were in
The region of interest from the Oxytocin receptor gene
(OXTR rs53576) was amplified by PCR using a forward
AC-30). Typical PCR reactions contained between 10 and
100ng genomic DNA template, 10pmol of forward and
reverse primers. PCR was carried out in the presence of 5%
DMSO with 0.3 U of BioThermAB polymerase (GeneCraft,
Munster, Germany) in a total volume of 30ml using the
following cycling conditions: initial denaturation step of
3min at 958C, followed by 40 cycles of 30s at 958C, 30s at
608C, 1min at 728C and a final extension step of 3min at
728C. To determine the A/G polymorphism, PCR fragments
were sequenced using the forward primer and dye termi-
nator chemistry (BigDye v3.1, Applied Biosystems). The
genotype distribution (n¼17 AA, n¼71 AG, n¼89 GG)
was in Hardy–Weinberg equilibrium. Because of the skewed
distribution AA and AG genotypes were combined in the
analyses. The distributions of 5HTT SLC6A4 and OXTR were
Table 1 presents the means, s.d. and bivariate correlations for
the main variables. OXTR and 5-HTT genotypes were not
associated with age of child, maternal educational level,
depression, maternal sensitivity, or marital discord (Table 1).
Mothers with a higher educational level appeared signifi-
cantly more sensitive to their children [r (157)¼0.38,
P<0.01] and less depressed [r (157)¼?0.19, P¼0.02] but
educational level was not related to marital discord. Marital
discord was related to depression [r (157)¼0.33, P<0.01].
The results of the analysis of variance of maternal
sensitivity with OXTR and 5-HTT SLC6A4 as factors and
maternal education, depression and marital discord as
covariates are presented in Table 2. Controlling for maternal
education, depression and marital discord, both OXTR
[F (1, 152)¼4.32, P¼0.04, partial ?2¼0.03] and 5-HTT
[F (1, 152)¼4.67, P¼0.03, partial ?2¼0.03] genes were
significantly associated with maternal sensitivity. Mothers
with OXTR AA or AG genotypes were less sensitive than
mothers with the GG genotype, and mothers with 5-HTT ss
were less sensitive than mothers with 5-HTT sl or ll
(Table 1). The interaction between OXTR and 5-HTT
genes, and the two-way and three-way interactions of the
genotypes with marital discord and depression did not
contribute significantly to the prediction. 5-HTT ll vs ss/sl
did not contribute significantly to the prediction of maternal
sensitivity in a separate analysis.
These results point to independent genetic effects on
maternal sensitivity of 5-HTT SLC6A4 and OXTR rs53576
polymorphisms, taking into account differences in educa-
tional level, depression and marital discord. We found lower
levels of sensitive responsiveness to their toddlers in parents
with the potentially less efficient variants of the serotonergic
and oxytonergic system genes. The genetic effects did not
interact with depression or the quality of the marital
relationship and neither depression nor the marital relation-
ship was associated with the genotypes examined in the
130SCAN (2008)M. J.Bakermans-Kranenburg and M.H. van IJzendoorn
current study. Thus, differences in sensitive parenting appear
to be associated with molecular genetic differences that may
implicate the production of oxytocin. Sensitive parenting is a
well-documented crucial determinant of young children’s
socio-emotional development with long-lasting
quences (Cassidy and Shaver, 1999; Sroufe et al., 2005;
Belsky et al., 2006), underscoring the relevance of our
Given the important role of the oxytocin system in
affiliative relationships OXTR is an excellent target in a
candidate gene approach involving parental caregiving of
offspring (Carter, 1998). Oxytocin not only has a critical role
in birth and lactation but also in the emergence of an
intimate bond with offspring, as it may lower feelings of
stress and fear (Carter, 1998; Young, 1999, 2001; Numan,
2006; Emiliano et al., 2007). Beyond the reduction of anxiety
oxytocin is suggested to have specific rewarding or hedonic
effects that may facilitate parenting (Numan and Insel,
2003). Our study is one of the first suggesting functional
implications for GG vs AG and AA variants of OXTR,
although the underlying processes linking variants of the
OXTR gene to actual oxytocin levels in humans have not yet
been clarified. In previous studies, variations in OXTR have
been related to autism. In a study in the Chinese Han
population preferential transmission of A over G was found
for rs53576 (Wu et al., 2005), indicating genetic vulnerability
to autism in carriers of the A allele?the same genotypic
variant that was related to lower levels of sensitivity in our
study. Replication in a Caucasian sample showed preferential
transmission of G over A at rs2254298 for children with
autism, but no significant association with rs53576 (Jacob
et al., 2007). These findings point to OXTR as an excellent
candidate for mediating genetic vulnerability to autism, but
they also indicate its potential for studies on the association
with sensitive parenting, which presupposes awareness of
and empathy with children’s needs and subtle emotional
In contrast surprisingly little evidence supporting the
significance of 5-HTT genes for parenting has been reported
(Numan and Insel, 2003). Serotonin has been associated
with negative emotions, such as anxiety or stress, although
meta-analyses on linear relations between 5-HTT SLC6A4
and anxiety related traits have shown somewhat divergent
results (Sen et al., 2004; Munafo et al., 2005). Here we
suggest that 5-HTT SLC6A4 is associated with parenting
through its potential influence on the oxytonergic system
as we did exclude the possibility that its influence would be
through its associations or interactions with maternal
The influence of genetic differences in 5-HTT (3%
explained variation) and OXTR (3% explained variation)
genes on parenting is much smaller than the association
between sensitive parenting and parental educational level
(15% explained variation). As Kagan et al. (2007) recently
argued, most psychological traits and behaviors may be
better explained by a combination of basic characteristics
such as gender and socio-economic status than by genetic
markers alone, although including both genetic and
environmental factors might predict such outcomes in
specific sub-groups with most accuracy. The findings of
the current study illustrate this point in showing that lower
maternal educational level is more strongly associated
with less sensitive parenting than genes potentially related
noted that mothers’ sensitive interaction with their toddlers
production. Itshould be
Table 1 Descriptives and correlations among the variablesa
GG (n¼79) AG/AA (n¼80) ss (n¼38)sl/ll (n¼121)
Ms.d.M s.d.M s.d.tM s.d.Ms.d.t
Child age (months)
Table 2 Analysis of variance of maternal sensitivity with OXTR and 5-HTTLPR
as factors and maternal education, depression and marital discord as
Oxytocin andserotoningenes andparentingSCAN (2008)131
was observed during problem-solving tasks potentially
eliciting differences in sensitive instruction, which might
explain its association with educational level. Moreover,
the more accurate assessments of genetic factors compared
with environmental influences may lead to less comparable
The role of genetic factors may also be dependent on
the presence or absence of stressful life circumstances, with
an increasing influence of hormonal effects on parenting in
deprived contexts with low social support (Repetti et al.,
2002). Numan and Insel (2003) argue that in primates
(as compared with rats) the balance between size and role
of the medial pre-optical area and the neocortex has shifted
in favor of the latter (Keverne, 2001). Primate parenting
might therefore be under stronger cognitive than hormonal
control, at least in normal circumstances (Numan and Insel,
2003; Kagan et al., 2007). However, the medial preoptic area
(MPOA) of the hypothalamus might still be involved by
signaling the level of maternal motivation to the neocortex,
which uses this input in the development of complex
voluntary response strategies (Numan and Insel, 2003).
Associations between serotonin and oxytocin system genes
and parenting might be most pronounced but not limited
to mothers in deprived settings, characterized by, for
example, high degrees of stress or marital discord. The
association between the 5-HTT ‘s’ allele and depression
under conditions of environmental adversity (Caspi et al.,
2003) is a replicated finding (Uher and McGuffin, 2008).
The absence of a significant gene–environment (GxE)
interaction in our study does not support the claim that in
certain (deprived) environments the role of hormones on
behavior is more pronounced, but it should be noted
that our sample is rather homogeneously well-educated, and
major deprivation is absent. In a previous report on the same
sample we found a negative impact of daily hassles on
parental sensitivity (Van IJzendoorn et al., 2007). Including
daily hassles as covariate in the current analyses did not
change the results. Better assessment of the environment
as well as more intense levels of environmental stress or
deprivation might however uncover GxE interactions that
were not apparent in the current study.
It has been noted that the influence of oxytocin might be
most important immediately after birth, for establishing
the bond between mother and offspring instead of
maintaining this bond at a later stage (Fahrbach et al.,
1985; Feldman et al., 2007; Insel and Harbough, 1989).
In the current study sensitive parenting was measured at
23 months. In order to assess the role of hormonal
mechanisms such as the oxytonergic system some time
after birth, Numan and Insel (2003) proposed to compare
the sensitivity of adoptive mothers with the sensitivity of
biological mothers to their offspring. Studying adoptive and
non-adoptive parents from similar backgrounds, Juffer
(1993) reported the absence of large differences in sensitive
parenting. The influence of oxytocin caused by parturition
and lactation may, therefore, be overridden by other
mechanisms of a more cognitive nature.
Although the oxytonergic system might thus not be a
necessary or sufficient condition for sensitive parenting,
experimental research showing that oxytocin improves
‘mind reading’ suggests that oxytocin nevertheless may
facilitate parental sensitivity at any stage in parents’ lives and
not only during the period around birth. In a double-blind
placebo controlled study on 30 adult males, Domes and
colleagues (2007) found that after intranasal administration
of a single dose of oxytocin participants were substantially
better able to infer the affective mental state of others
from subtle social cues from the eye region in a standard
paradigm, the Reading the Mind in the Eyes Test. The
authors state that reading the mind of an interactive partner
is a cornerstone of all human interactions, which would also
pertain to parenting. The definition of sensitive parenting
explicitly includes the reading of the child’s attachment
needs from subtle facial or other non-verbal signals as a
first and important step to responding in a prompt and
adequate manner (Ainsworth et al., 1978; Egeland et al.,
1990; Sroufe et al., 2005).
Our study is limited in several ways. First, generalization
of our findings may be limited to samples similar to the
rather homogeneous middle-class sample included in the
current study. Moreover, the families in the current study
had an externalizing toddler (75th percentile or above on the
CBCL), and our findings may only apply to parents who
perceive their children as difficult and non-compliant, and
who already at an early stage have difficulty managing their
children. It is important to note, however, that the families
in our study were two-parent families from predominantly
well-educated background and without psychiatric disor-
ders. Nevertheless, replication in unselected samples is
Second, although our sample size is relatively large
compared with other studies including observational mea-
sures of parenting, our study may nevertheless lack power to
detect gene–gene or gene–environment interaction effects.
Moreover, the OXTR AA and AG genotypes were combined
in the analyses, as were the 5-HTT sl and ll genotypes
(similar to, e.g. Kaufman et al., 2004; Battaglia et al., 2005;
Hayden et al., 2007; Young et al., 2007; but see Hariri et al.,
2002; Caspi et al., 2003 for combined ss/sl vs ll genotypes).
In our study 5-HTT ss/sl vs ll did not contribute significantly
to the prediction of maternal sensitivity. It should be noted
that the 5-HTT SLC6A4 gene possesses several other
polymorphic loci affecting its expression and function that
were not included in this study (Wendland et al., 2006).
Third, because 5-HTT and OXTR genes have been
associated with other forms of social behavior and mental
states (Uher and McGuffin, 2008), it is unclear how specific
and direct their influence is on sensitive parenting. It is
possible that both genes affect interpersonal sensitivity more
generally, which may in turn make parents more sensitive
132 SCAN (2008)M. J.Bakermans-Kranenburg and M.H. van IJzendoorn
to their offspring. Alternatively, the genes might be
associated with affective states that promote or hamper
the display of sensitive parenting. Further research is needed
to clarify the process underlying the association found in
the current study.
Last, we did not assess oxytocin levels directly, but variants
of the oxytocin receptor gene that have not yet been shown
to be functional. In a promising line of research Carter
and her colleagues (2007) showed that oxytocin might be
extracted from saliva samples, with detectable variations
of oxytocin concentrations in saliva depending on lactation
in mothers and massage in male subjects. Oxytocin levels
in saliva were however low and assessments labor-intensive.
In the near future it may become easier to measure salivary
oxytocin as a biomarker for affiliative behavior in humans,
in particular in parenting, which would enable direct tests
of the association between oxytocin and sensitive parenting
suggested in the current report.
In conclusion, the present study is the first to suggest
independent effects on maternal sensitivity of 5-HTT and
OXTR genes in humans. Taking into account differences
in maternal educational level, depression and marital
discord, we found that parents with the possibly less efficient
variants of the serotonergic and oxytonergic system genes
showed lower levels of sensitive responsiveness to their
toddlers. The current study is among the first to examine the
molecular genetic basis of human parenting. The findings
support previous results of environmental effects on
sensitive parenting, but additionally point to molecular
genetic differences that may be implicated in the production
of oxytocin as a factor explaining differences in sensitive
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