Sleep, emotional and behavioral difficulties in children and adolescents
Alice M. Gregorya,*, Avi Sadehb,c
aDepartment of Psychology, Goldsmiths, University of London, UK
bThe Adler Center for Research in Child Development and Psychopathology, Department of Psychology, Tel Aviv University, Israel
a r t i c l e i n f o
Received 27 December 2010
Received in revised form
8 March 2011
Accepted 23 March 2011
Available online 15 June 2011
s u m m a r y
Links between sleep and psychopathology are complex and likely bidirectional. Sleep problems and
alteration of normal sleep patterns have been identified in major forms of child psychopathology
including anxiety, depression and attention disorders as well as symptoms of difficulties in the full range.
This review summarizes some key findings with regard to the links between sleep and associated
difficulties in childhood and adolescence. It then proposes a selection of possible mechanisms underlying
some of these associations. Suggestions for future research include the need to 1) use multi-methods to
assess sleep; 2) measure sleep in large-scale studies; 3) conduct controlled experiments to further
establish the effects of sleep variations on emotional and behavioral difficulties; 4) take an interdisci-
plinary approach to further understand the links between sleep and associated difficulties.
? 2011 Elsevier Ltd. All rights reserved.
Sleep disturbances in children and adolescents are common
(e.g.,1,2). It is increasingly apparent that sleep disturbances are
associated with both emotional (e.g., anxiety and depression) and
behavioral (e.g., attention and conduct) difficulties in children and
adolescents.3Understanding more about co-occurring difficulties
can facilitate understanding of the developmental progression of
difficulties, aid researchers and clinicians in the early identification,
prevention and treatment of difficulties as well as inform associ-
ated issues such as nosology (the classification of disorders). Given
the known importance of sleep inyouth,4as well as the importance
of having detailed knowledge of associations with other pheno-
types, this review presents a selection of key empirical findings on
the links between sleep and emotional and behavioral difficulties in
children and adolescents. The review begins with a discussion of
issues surrounding the definition and measurement of sleep
disturbances. Concurrent links between sleep and emotional and
behavioral difficulties are then described e followed by the
presentation of longitudinal associations. A selection of possible
mechanisms underlying associations is then described. The review
ends with a description of future challenges for the field. These
include the need to: 1) use multi-methods to assess sleep; 2)
measure sleep in large-scale studies; 3) conduct controlled exper-
iments to further establish the effects of sleep variations on
emotional and behavioral difficulties; and 4) take an interdisci-
plinaryapproach tofurther understand the links between sleep and
Defining and measuring sleep disturbances
Perhaps the biggest challenge when assimilating literature on
sleep and associated difficulties is the lack of consensus regarding
how to assess and define sleep disturbances. Three issues concern-
disturbancescantakemany forms.Forexample,adistinction canbe
drawn between dyssomnias (such as insomnia) and parasomnias
(such as sleep walking). Furthermore, the classification of such
disorders varies, depending on the system being followed e and
sleep disturbances are classified by the Diagnostic and Statistical
Manual for Mental Disorders5and the International Classification of
(e.g., sleeplessness) there is lack of consensus concerning what
constitutes a problem.7A final issue concerns measurement. Sleep
can be measured objectively using measures such as poly-
somnography (PSG) and actigraphy (for a discussion of the role of
* Corresponding author. Tel.: þ44 (0)20 7919 7959; fax: þ44 (0)20 7919 7873.
E-mail addresses: email@example.com (A.M. Gregory), firstname.lastname@example.org
cTel.: þ972 3 6409296; fax: þ972 3 6409547.
Contents lists available at ScienceDirect
Sleep Medicine Reviews
journal homepage: www.elsevier.com/locate/smrv
1087-0792/$ e see front matter ? 2011 Elsevier Ltd. All rights reserved.
Sleep Medicine Reviews 16 (2012) 129e136
using questionnaires and sleep diaries. There are strengths and
weaknesses of each approach. For example, objective measures of
sleep may fail to capture the subjective sense of having a problem
with sleep; whereas the use of subjective measures alone does not
techniques can yield different results. For example, one study
showed that youth with depression had sleep disturbances as
Even within methodologies (e.g., questionnaires), conclusions can
differ depending on the precise procedure used. Indeed, child self-
reports of sleep disturbances have been shown to yield more sleep
problems as compared to parental reports of their children’s
sleep2,10although interestingly when focusing on clinical samples
the situation appears reversed (with parents reporting more diffi-
culties than children).11,12
Given a lack of consensus when defining and measuring sleep
problems, studies to date have used numerous measures and
definitions. Many studies have addressed a full range of ‘sleep-
related problems’ rather than specific sleep disorders. This is
particularlythe case as a numberof studies have capitalized on data
already collected in large-scale (e.g., epidemiological) studies
which have not assessed sleep thoroughly. This occurred partly
because, up until recently, sleep appears to have been considered
a secondary symptom of other problems rather than a phenotype
worthy of consideration in its own right. In this review numerous
conceptualizations of ‘sleep disturbances’, measured in different
ways, are considered.
Sleep and emotional problems
Links between sleep disturbances, anxiety and depression in
adulthood are well established.5In contrast, only relatively recently
has there been a wide interest in these associations within childhood
and adolescence. Within this field, as with sleep disturbances,
emotional problems have been conceptualized in different ways.
a single variable,3,13others distinguish between anxiety subtypes.14
Sleep and combined anxiety/depression
Studies combining anxiety/depression have reported associa-
tions with a range of different sleep disturbances. For example, in
a non-clinical sample, trouble sleeping was associated with parent
(but not teacher) reports of anxiety/depression in children when
theywere aged6 years and againwhen theywere aged11 years.13A
further study reported that nightmares within childhood were
associated with, amongst other symptoms, emotional difficulties.15
An additional study reported links between anxiety/depression and
a composite measure of sleep disturbance in participants assessed
between the ages of 4 and 15 years.3
Studies examining associations between sleep and anxiety/
depression have focused on different age groups. Interestingly,
of associations over time. For example, one study found that the
association between sleep and anxiety/depression was greater in
children aged 11 (odds ratio ¼ 9.7) as compared to when they were
aged 6 years (odds ratio ¼ 4.7).13Interestingly, an increase in the
magnitude of the correlation between sleep disturbance and
anxiety/depression from childhood (age 4 years, r ¼ 0.39) to
adolescence (age 13e15 years, r ¼ 0.52) was reported in a further
report.3One possible explanation for this trend is that sleep
disturbances may be more common in children than adolescents3
and hence perhaps more part of ‘normal development’ and less
significant/indicative of a problem (although it is important to note
that sleep difficulties in childhood have been linked to various
difficulties both concurrently and longitudinally, e.g.,3).
Sleep and anxiety
Further studies have focused on anxiety exclusively (rather than
community sample of adolescents, those with disturbing dreams
had higher anxiety scores as compared to those who infrequently
had such dreams.16It is important to note that not all studies report
community study of 8-year-olds found that self-reported anxiety
scores were higher in participants whose parents reported bedtime
resistance than in those who did not, but not for the other seven
In addition to studies examining community samples, a number
of reports have focused on clinical populations. One such study
addressed the prevalence of sleep-related problems in youth with
anxiety disorders e finding that one or more sleep-related problem
was reported in 88% of these participants.18While most studies do
not differentiate between weekday and weekend sleep, this
distinction was made in a sample comprising children with clini-
cally-diagnosed anxiety and those who had never sought clinical
intervention.19Amongst interesting findings, anxious children
reported going to bed later and having less sleep than non-anxious
children on school nights. Furthermore, anxious children reported
falling asleep more quickly and experiencing fewer night wakings
during the night on weekends as compared to weeknights.
Although most studies on the links between sleep and anxiety
have focused on subjective measures of sleep (primarily using
questionnaire measures), a few studies have considered objective
measures. For example, a clinical study using objective measures of
sleep in youths experiencing anxiety disorders20found that when
sleep was assessed using EEG, those with anxiety appeared to have
poorer sleep than did those with depression and controls. For
example, those with anxiety experienced more night wakings as
compared to those with depression; and during the second night in
the laboratory had a longer sleep latency as compared to both
controls and those with depression.
A number of studies have distinguished subtypes of anxiety and
one study reported links between sleep and obsessive compulsive
disorder.11A further study examined EEG sleep profiles in adoles-
cents diagnosed with obsessive compulsive disorder (OCD).21There
were differences in sleep between matched controls and those
diagnosed with OCD (e.g., the latter slept for a shorter total period
and less time was spent in stage 2 sleep). Despite this finding, it is
attention deficit hyperactivity disorder
autism spectrum disorders
child behavior checklist
major depressive disorder
obsessive compulsive disorder
pervasive developmental disorders
periodic limb movements in sleep
rapid eye movement
A.M. Gregory, A. Sadeh / Sleep Medicine Reviews 16 (2012) 129e136
noteworthy that in a community sample, the correlation between
sleep and OCD symptoms in adolescents was not significant.14
Certain types of anxiety as compared to others may be more
stronglyassociated with sleep. Indeed, in a communitysample of 8-
year-olds, self-reported sleep disturbances appeared to be more
strongly associated with certain types of anxiety (e.g., school
phobia) than others (e.g., social phobias).22A further study reported
that during childhood, sleep difficulties were associated with all
types of anxiety examined; within adolescence, sleep disturbance
appeared to be associated with certain types of anxiety (general-
ized anxiety, panic/agoraphobia and social anxiety) but perhaps not
others (obsessive compulsive symptoms and separation anxiety).14
Clinical studies comparing different anxiety subtypes also suggest
that sleep difficulties may be more strongly associated with certain
disorders (e.g., generalized anxiety disorder) as compared to others
(e.g., social anxiety).18,23
The issue of developmental change has been investigated with
regard to the links between sleep and anxiety. One study found that
in contrast to research focusing on combined anxiety/depression,
there did not appear to be a stronger association between sleep and
anxiety in adolescents as compared to children.14
Sleep and depression
As with anxiety, studies focusing on ‘pure’ depression (rather
than combined with anxiety) have found associations with subjec-
tive reports of sleep disturbances. Indeed, sleep complaints are
common in prepubertal children and adolescents with depression
depression, associations may be influenced by age. For example, in
a comparison of children and adolescents with major depressive
disorder (MDD) hypersomnia was reported less commonly in the
in a study mentioned previously, in contrast to the association with
anxiety, the correlation between symptoms of sleep problems and
to adolescents (r ¼ 0.58).14
In addition to subjective reports of sleep disturbance, objectively
assessed sleep disturbances have also been investigated in associa-
tion with depression. Studies have revealed mixed results e with
adolescents with depression as compared to controls.9,26,27Other
studies have reported objective sleep differences between youths
with and without depression. For example, in one study incorpo-
rating PSG, 21 children showing symptoms of depression were
sleep latencyand REM sleep duration and a higher number of night-
wakings. This findingof shorter REM sleep latency (often considered
a biological marker of endogenous depression) has been reported in
other samples of children29,30and adolescents31suffering depres-
sion.Overall,discrepanciesbetween studies may bepartlyexplained
by differences in the age of participants and severity of depression
symptoms (for a review, see elsewhere32).
Studies using other objective sleep assessment methods shed
additional light on this topic. For example, an actigraphic study of
resteactivitycycles in childrenwith MDD found that in comparison
to controls these children present damped circadian amplitude and
lower light exposure and daytime activity levels.33Such findings
suggest that alterations in circadian rhythms could underlie
changes in sleep architecture and overall clinical presentation in
children and adolescents with depression.
Despite mixed reports, overall, it appears that associations
between sleep and depression are stronger when focusing on
subjective as compared to objective reports. Indeed, a study
assessing both subjective and objective sleep in youth suffering
MDD, found that depressed participants as compared to controls
reported poorer sleep quality, claimed to experience a higher
number of night awakenings, estimated that they were awake
longer during the night and reported more difficulty waking.9In
contrast, sleep as assessed by EEG did not appear to be worse for
depressed as compared to control participants (see also20). Similar
findings have been reported for prepubertal children (e.g.,27).
Considering all studies in this field, the only relativelyconsistent
finding emerging from the cumulative subjective and objective
sleep studies is related to increased sleep latency.24Reduced REM
sleep latency may also be found in depressed youth.34
Sleep and behavioral problems
Sleep and attention deficit hyperactivity disorder (ADHD)
The links between sleep and behavioral problems or disorders
have also been under scrutiny over the last 3 decades. In this
context, the topic of ADHD and related symptoms and behaviors
has drawn most scientific attention. Because a number of review
and meta-analytic papers have been published recently, (e.g.,35e37)
only a brief summary is included here.
Studies based on subjective reports have consistently reported
that sleep problems are more common in children diagnosed with
ADHD in comparison to controls (e.g.,37). These problems include
bedtime resistance, sleep initiation difficulties, and night-wakings.
ADHD and related symptoms have been consistently reported in
children with sleep disorders including periodic limb movements
in sleep (PLMS) and sleep-disturbed breathing (for a review, see
elsewhere38). PSG-based studies comparing children with ADHD
and controls have provided inconsistent results. With regard to
sleep architecture, one meta-analytic review of PSG studies
concluded that there were no consistent significant differences
between children with ADHD and controls.36The only consistent
and significant finding in this meta-analysis was that children with
ADHD are more likely than controls to suffer from PLMS. A second
meta-analytic review concluded that children with ADHD have
lower sleep efficiencies, more sleep stage shifts and increased
apnea-hypopnea index in PSG studies.37The discrepancy between
the conclusions drawn is likely to be due in part to the different
studies included in the two reports. Studies using actigraphy have
also revealed some additional features including high variability in
sleep schedules in children with ADHD as compared to controls
(e.g.,39). Other actigraphic studies have shown that children with
ADHD have shorter sleep time and that their sleep is more frag-
increased daytime sleepiness as compared to others (e.g.,40). Sleep
deprivation or disruption may lead, in typically developing chil-
dren, to compromised alertness and neurobehavioral functioning
(e.g.,4,41,42). It is therefore possible that sleep problems contribute
to the aetiology and exacerbation of symptoms of ADHD.
40). Children with ADHD may also experience
Sleep and aggression, conduct disorder and addiction
Other behavioral problems such as aggression, conduct disor-
ders, as well as addiction have received less attention, although
there are indications that these disorders are also linked to sleep
problems. Many studies, based on subjective or parental reports
find associations between sleep problems, insufficient sleep and
behavioral problems. For example, sleep-disordered breathing has
been associated with behavioral problems including aggression
(e.g.,43). Other sleep issues such as sleeping less than others have
also been associated with behavioral difficulties (e.g.,44,45). Studies
using objective measures of sleep (actigraphy) and teachers’ or
parental ratings of behavior problems have also reported signifi-
cant correlations between short sleep time or poor sleep quality
and behavioral difficulties in school-age children.46,47Of note,
A.M. Gregory, A. Sadeh / Sleep Medicine Reviews 16 (2012) 129e136
a similar study in adolescents failed to find such relationships48e
again, potentially highlighting the importance of age when
considering associations between sleep and associated difficulties.
In adolescence, substance abuse and other risk behaviors have also
been linked to sleep problems (e.g.,49,50).
Sleep and other difficulties
Pervasive developmental disorders (PDD), autism, or autism
spectrum disorders (ASD) and related non-specified neuro-
developmental disorders have also been associated with significant
sleep problems (e.g.,51e53). Studies of children with PDD or ASD
consistently show higher prevalence of sleep problems in
comparison to typically developing children or children with other
developmental disabilities. Sleep problems are reported in between
25% and 80% of the children depending on sample composition and
definition of sleep problems.53Studies have also demonstrated
associations between the severityof the ASD and the severityof the
Studies assessing children with ASD in comparison to controls
using actigraphy have mostly reported poorer sleep as indicated by
increased sleep latency and night-wakings, lower sleep efficiency
and early morning risetime (e.g.,55,56). It is noteworthy that the
identified unique sleep features of childrenwith ASD are notalways
consistent across studies. Some studies report sleep schedule
related problems (increased sleep latency, earlier morning rise-
time) whereas other studies report poor sleep quality (increased
night-waking, lower sleep efficiency).
PSG studies have also demonstrated unique sleep characteristics
in childrenwith ASD and related disorders (e.g.,57,58). These reports
have highlighted differences from typically developing children
including reduced REM sleep latency and total sleep time. While
findings are not all consistent across studies, the overall impression
is that the sleep of children with ASD is substantially different from
typically-developing children, and the unique characteristics of
sleep in these children may be related to issues such as the severity
of the neurodevelopmental disorder and comorbidity with other
disorders and associated features.
Sleep abnormalities have also been linked to a host of other
difficulties. These include Tic disorder, where PSG studies suggest
that sleep difficulties may include increased arousals during the
sleep period (e.g.,59).
In addition to highlighting concurrent associations, researchers
have also investigated longitudinal associations between sleep and
other phenotypes. Such studies encompass different time periods
spanning a year or so60to over a decade.61These studies suggest
that sleep disturbances in childhood or adolescence predict
a whole host of later difficulties (e.g.,3,50), with some studies
reporting this link even when adjusting for the stability of diffi-
culties over time (e.g.,3,62).
Sleep and emotional problems
with emotional problems. These studies suggest that sleep distur-
bances (conceptualized in various ways) in childhood or adoles-
cence predict later anxiety63and depression.62,64It is important to
note that not all studies have reported significant associations. For
and in another, persistent sleep disturbances in childhood did not
predict depression disorders in adulthood.63
Longitudinal studies of sleep and emotional difficulties have
conceptualized sleep disturbances in various ways. A number of
studies have defined sleep disturbance using items from the Child
Behavior Checklist (CBCL),65a measure of behavioral difficulties in
youth which is commonly included in large-scale studies (e.g.,
than others’) are more robust predictors of later difficulties than
others (e.g., ‘sleeps more than others’).45Few large-scale longitu-
dinal studies have defined sleep thoroughly because sleep is typi-
cally not well assessed in such studies of health and development.
tested just one direction of effects (e.g., sleep predicting later diffi-
culties). Such studies investigating this issue are limited in that they
do not allow testing of the converse hypothesis (e.g., that early
difficulties predict later sleep disturbances). Associations are likely
to be bidirectional, although certain studies investigating this issue
have found that sleep disturbances predict later emotional diffi-
culties, but provide less support for the converse association.3,66
Another study investigated the order of effects of insomnia,
anxiety and depression in a community sample of adolescents.67
Retrospective reports indicated that anxiety disorders precede
insomnia in 73% of comorbid cases whereas insomnia preceded
depression in 69% of comorbid cases. The authors concluded that
sleep difficulties may be associated with anxiety and depression in
e.g.,63). One explanation for this general conclusion focuses on
phenomenological differences between anxiety and depression.
Indeed, hyperarousal, which according to the tripartite model of
anxiety and depression is associated with the former but not the
latter difficulty,68is sometimes considered an important feature of
insomnia.69Hyperarousal could therefore be a vulnerability factor
for anxiety and insomnia (but not depression, although not all data
support this suggestion).70
Sleep and behavioral problems
Fewer studies have examined longitudinal links between sleep
and behavioral problems including attention problems (e.g.,71) and
addiction.49,50One study in this area showed that the persistence of
sleep problems over a two-year period in school children predicts
amongst other things, behavior problems.72A further study
showed that mother reports of sleep problems experienced during
childhood (3e8 years) predicted early onset of drug use (particu-
larly in boys).50
Although previous longitudinal studies of sleep and associated
phenotypes tend toignore factors that could mediate and moderate
associations e these issues need consideration. Indeed, one study
highlighted sex differences in the association between sleep and
later substance use, with sleep disturbances in childhood predict-
ing alcohol, cigarette and marijuana use among adolescent boys but
only alcohol use among adolescent girls.50An additional study
examining the longitudinal link between sleep and adjustment
highlighted the importance of race and socioeconomic status as
potential moderators of the association.73Furthermore, a study of
the trajectories of sleep disturbances and externalizing (aggression
and rule-breaking) behaviors from ages 5e9 years, found that sleep
and externalizing behavior trajectories were only associated in
children whose mothers had reported that they displayed high
temperamental resistance to control during infancy.44
Summary: sleep and associated difficulties
A review of the literature reveals that the recent increase in
interest in the links between sleep difficulties and associated
problems in youth is warranted. Indeed, sleep disturbances have
A.M. Gregory, A. Sadeh / Sleep Medicine Reviews 16 (2012) 129e136
been associated with a whole host of other difficulties concurrently
and may also represent risk indicators for the emergence of further
problems later in life. Additional research is needed to confirm
emerging trends (such as developmental changes in the magnitude
of associations over time and the precise objective sleep differences
between those with and without various disorders). An additional
priority for future work is to understand the mechanisms under-
lying links between sleep and associated difficulties e and it is to
this area of research that we now turn.
Mechanisms underlying associations
When explaining the associations between sleep disturbance
and other difficulties it is important to reflect on the issue of
nosology. Sleep disturbances are considered symptoms of a range
of other disorders (including generalized anxiety disorder and
major depressive disorder) as well as distinct diagnoses (see DSM-
IV5). This topic has been widely discussed and despite symptom
overlap, there are strong arguments for not dismissing sleep diffi-
culties as secondary to other difficulties.74Indeed, sleep difficulties
may precede other problems and treatment of sleep problems may
reduce symptoms of other disorders.74Regardless of whether sleep
disturbances are considered symptoms of other disorders or
separate diagnoses, it is important to try to understand this overlap
in order to gain a fuller understanding of sleep problems them-
selves and the difficulties with which they are associated.
One explanation for some of the associations reported concerns
the methodological issue that sometimes the same raters (e.g.,
parents) report both sleep problems and associated traits. This
allows for the possibility that rater bias (or response set) could
account for some of the associations reported, although not all
associations can be accounted for in this way. For example, some
studies have reported associations between variables assessed by
different raters (e.g., parent reports of sleep disturbances and child
self-reports of emotional difficulties).17Furthermore, other studies
have examined links between objective measures of sleep and
reports of psychiatric difficulties.20
One type of study which has been informative with regards to
reasons underlying associated traits involves twins (for a discussion
of twin studies, see elsewhere75). Twin studies typically compare
the similarity of identical and non-identical twins. This information
can be used to draw inferences about the magnitude of genetic and
environmental influences on the association between traits. There
have been a handful of twin studies in children reporting on sleep
and associated traits e and one study found that parent-reports of
sleep disturbances in 3-year-olds appeared to be genetically unre-
lated to all other scales assessed, including oppositionality; with-
drawn/depressed behavior; aggressive behavior; anxious behavior
and overactivity.76In contrast, common ‘shared environmental
factors’ (i.e., those environmental factors which act to make indi-
of difficulties. A further twin study of the links between sleep
disturbance and depression symptoms in 8-year-olds suggested
that the association was largely explained by genes.17When
examining longitudinal associations between sleep at 8 and
depression symptoms at 10 years, genes also appeared to play an
important role.66Twin studies focusing on adult participants have
also examined the associations between sleep and associated traits
(e.g.,77,78) e although caution should be taken before extrapolating
findings from adults to children. This is because of factors including
developmental changes with regards to sleep and genetic influ-
ences on certain aspects of sleep.79Although standard twin studies
are informative in estimating the magnitude of genetic influences
on traits, they do not tell us much about specific genes that influ-
ence traits, and this information typically comes from elsewhere
(e.g., association and linkage studies).
Specifying genetic and environmental factors
The specific genes implicated in the overlap between various
phenotypes and sleep disturbance depends on the variable with
which sleep is being associated. For example, genes involved in the
serotonin pathways are likely to play a role in the associations
between sleep and anxiety given the role that serotonin plays with
regards to each phenotype (e.g.,
(MAO-A; an enzyme involved in the catabolism of monoamines) is
a good candidate to further explore with regards to the links
between sleep and aggression because it has been associated with
both phenotypes previously.82,83The functional polymorphism of
the catechol-O-methyltransferase (COMT) gene has been impli-
cated in the links between sleep and ADHD.84Complex phenotypes
are likely to be influenced by multiple genes of small effect size,
hence there is a clear need tofurther specifygenesinvolved in sleep
disturbances and associations with other traits.
As with the need to further specify genes, it is also essential to
elucidate additional environmental factors that account for the
association between difficulties. Indeed, one study found that both
family disorganization and maternal depression each correlated
moderately with both sleep disturbance and anxiety symptoms in
children aged 3 and 4 years and accounted for some of the asso-
ciation between the two difficulties.85Other candidate environ-
mental influences include being a bully victim, which is associated
with both sleeping poorly and feeling sad86and socioeconomic
status which is associated with awhole hostof difficulties including
poor sleep (e.g.,87,88).
The role of parenting in sleep development and sleep problems
has been repeatedly demonstrated, particularly in early childhood
(e.g.,89,90). Within this arena, one study focusing on adolescents
with a history of substance abuse found that perception of lower
levels of parental involvement was associated with lower sleep
efficiency and increased time in bed e an association that was
mediated through psychological distress.91A further study found
that whereas in young children (aged 5e11 years), greater levels of
parental warmth was associated with longer sleep during the
week; in older participants (aged 12e19 years) stricter parental
rules were associated with longer weekday sleep.92Such findings
emphasize the need to consider child sleep problems in the context
of the family.93As with sleep disturbances, different aspects of
parenting are also known to be associated with emotional and
behavioral difficulties (e.g.,3). It is quite conceivable that parenting
influences explain some of the sharedvariability between sleep and
Stress and trauma have also been implicated in altered bio-
behavioral functioning and have also been associated with both
psychopathology and sleep disorders.94,95Stressful life events or
traumatic history could therefore be an additional bridge between
sleep and psychopathology.
While genetic and environmental influences are commonly
considered separately, it is likely the genetic and environmental
effects. Indeed, interactions between genes and environmental
factors are shown for difficulties including sleep quality96as well as
80,81). Monoamine oxidase A
A.M. Gregory, A. Sadeh / Sleep Medicine Reviews 16 (2012) 129e136
various associated traits (including depression and behavioral
Pathways through which genetic and environmental factors work
As well as further understanding genetic and environmental
influences on sleep disturbances and associated variables, further
researchneeds toelucidate the pathways bywhich these influences
have their effects. Indeed, genetic/environmental influences impact
upon hormones as well as neural and psychological processes
known to be associated with sleep and behavioral/emotional
Research has revealed melatonin abnormalities in children with
ADHD98or with ASD (e.g.,99). These altered melatonin secretion
patterns may explain sleep schedule difficulties seen in children
with ASD and this hypothesis is supported by studies showing the
positive effects of melatonin treatment on sleep in children with
ADHD (e.g.,100) and in children with ASD (e.g.,101).
The environmental influence, that is light, influences melatonin
production, and blind individuals (with limited light perception)
are more prone to suffer from sleep-schedule disorders than are
fully sighted individuals. The dynamics of the links between sleep-
schedule disorder and aggressive behaviors were demonstrated in
a case report of a blind adolescent.102
A further hormone likely to be involved in the association
between sleep and difficulties in other areas is cortisol. Stress is
a response to a perception of imminent threat which requires vigi-
lance and sleep is an antagonistic behavior. Stress is associated with
higher levels of corticotropin releasing hormone, which may have
axis which controls reactivity to stress is likely to be involved in the
association between sleep and emotional difficulties.
Neuroimaging studies on brain metabolism and activation
following sleep deprivation and recovery sleep have shed light on
the links between sleep and emotion regulation.104A relevant
neuroimaging study demonstrated that participants who had been
sleep deprived for 35 h showed a greater amygdala response to
negative emotional stimuli as compared to participants who had
not been sleep deprived.105It was also found that sleep-deprived
participants, as compared to controls, showed weaker functional
connectivity between the amygdala and the medial-prefrontal
cortex (a brain region which is believed to help in regulating
amygdala function) e suggesting that sleep-deprived participants
had less ability than others to moderate emotional responses. The
authors speculated that these results could support the proposal of
causal links between sleep and mood disorders.
associated with sleep and co-occurring difficulties comes from the
studies of the effects of sleep deprivation on emotion recognition
emotional expression recognition in sleep deprived and control
healthy adults. Their findings suggested that sleep deprivation
resulted in reduction in the recognition of angry and happy
emotional expressions (when these expressions were of moderate
intensity). Taken together, studies focusing on sleep deprivation
suggest that sleep is essential for proper emotional regulation and
that sleep disruptions or insufficient sleep could lead to compro-
mised emotional regulation which is one of the core features of
many difficulties associated with sleep.104
106). van der Helm et al. assessed the accuracy of facial
Summary and future challenges
Sleep issues are ubiquitous in children with emotional and
behavioral problems. These associations appear when measuring
traits in the full range as well as at the extremes e and occur when
assessing associations both concurrently and longitudinally. Asso-
ciations between sleep, emotional and behavioral difficulties are
likely bidirectional, with sleep problems or insufficient sleep
exacerbating emotional and behavioral difficulties; and, mood
disturbances, anxiety and stress compromising sleep patterns.
of participants e emphasizing the need to test hypotheses in
differentagegroups.The precise definitionsof sleep andemotional/
behavioral problems used also influence results. Indeed, where
sleep has been assessed in large-scale epidemiological studies,
suboptimal measures have often been used and there is a need to
include more widely validated measures of sleep in studies of this
type. More generally, refining definitions of psychopathology and
behavior problems has been an ongoing challenge in child psychi-
atryand related disciplines with significant implication for this area
of research. Discrepancy in sleep assessment methods also explains
contradictory findings e and videosomnography, actigraphy and
PSG, which are the most common objective methods toassess sleep
in youth, can provide distinct information.
The mechanisms underlying associations are slowly being
elucidated. Indeed, the use of different methodologies (e.g.,
prospective longitudinal studies; twin studies; experimental
studies) has highlighted genetic and environmental factors on both
emotional and behavioral difficulties and produced candidate
hormonal, neural and psychological mechanisms through which
genetic and environmental factors may exert their influences. Such
studies have also highlighted the possibility that shared mecha-
nisms (e.g., poor sleep and subsequent compromised emotional
regulation) can lead to a range of difficulties. Studies in this domain
also highlight the possibility that studying certainpopulations (e.g.,
thosewith visual impairment) may prove valuable in learning more
about links between sleep and associated difficulties.
In order to further understand the links between sleep and
emotional and behavioral difficulties, additional sleep intervention
and manipulation studies are required e to examine the possibility
of causal links and the therapeutic potential of sleep interventions
in repairing emotional and behavioral outcomes. Interdisciplinary
research (e.g., including twins in sleep manipulation studies and
collecting deoxyribonucleic acid (DNA) on those participating in
such studies) will go some way towards providing a more
comprehensive understanding of the links between sleep and
1) Sleep disturbances are linked to a host of emotional and
behavioral difficulties in children and adolescents;
2) These associations are likely to be bidirectional and
3) There are some inconsistencies in results depending on
the age of the children and whether sleep is assessed
subjectively or objectively;
4) Both genetic and environmental factors are likely to
contribute to the associations between sleep and
emotional and behavioral difficulties;
5) Genetic and environmental factors are likely to have
their influences via complex pathways, influencing
A.M. Gregory, A. Sadeh / Sleep Medicine Reviews 16 (2012) 129e136
Conflict of interest
The authors declare no conflict of interest.
Alice M. Gregory is supported bya Leverhulme Trust Fellowship.
We thank Liat Tikotzky for her valuable comments.
1. Kahn A, Van de Merckt C, Rebuffat E, Mozin MJ, Sottiaux M, Blum D, et al.
Sleep problems in healthy preadolescents. Pediatrics 1989;84:542e6.
2. Owens JA, Spirito A, McGuinn M, Nobile C. Sleep habits and sleep distur-
3. Gregory AM, O’Connor TG. Sleep problems in childhood: a longitudinal
study of developmental change and association with behavioral problems.
J Am Acad Child Adolesc Psychiatry 2002;41:964e71.
4. Sadeh A, Gruber R, Raviv A. The effects of sleep restriction and extension on
school-age children: what a difference an hour makes. Child Dev
5. American Psychiatric Association. Diagnostic and statistical manual of
mental disorders DSM IV. Washington, DC: American Psychiatric Associa-
6. American Academy of Sleep Medicine. International classification of sleep
disorders: diagnostic and coding manual. 2nd ed.; 2005. Westchester, IL.
7. Wiggs L. Are children getting enough sleep? Implications for parents.
Sociological Res Online 2007;12.
8. Sadeh A, Acebo C. The role of actigraphy in sleep medicine. Sleep Med Rev
9. Bertocci MA, Dahl RE, Williamson DE, Iosif AM, Birmaher B, Axelson D,
et al. Subjective sleep complaints in pediatric depression: a controlled
study and comparison with EEG measures of sleep and waking. J Am Acad
Child Adolesc Psychiatry 2005;44:1158e66.
10. Gregory AM, Rijsdijk FV, Eley TC. A twin-study of sleep difficulties in
school-aged children. Child Dev 2006;77:1668e79.
11. Storch EA, Murphy TK, Lack CW, Geffken GR, Jacob ML, Goodman WK.
Sleep-related problems inpediatric
J Anxiety Disord 2008;22:877e85.
12. Alfano CA, Pina AA, Zerr AA, Villalta IK. Pre-sleep arousal and sleep prob-
lems of anxiety-disorderedyouth.
13. Johnson EO, Chilcoat HD, Breslau N. Trouble sleeping and anxiety/depres-
sion in childhood. Psychiatry Res 2000;94:93e102.
14. Alfano CA, Zakem AH, Costa NM, Taylor LK, Weems CF. Sleep problems and
their relation to cognitive factors, anxiety, and depressive symptoms in
children and adolescents. Depress Anxiety 2009;26:503e12.
15. Schredl M, Fricke-Oerkermann L, Mitschke A, Wiater A, Lehmkuhl G.
Longitudinal study of nightmares in children: stability and effect of
emotional symptoms. Child Psychiatry Hum Dev 2009;40:439e49.
16. Nielsen TA, Laberge L, Paquet J, Tremblay RE, Vitaro F, Montplaisir J.
Development of disturbing dreams during adolescence and their relation to
anxiety symptoms. Sleep 2000;23:727e36.
J Dev Behav Pediatr
17. Gregory AM, Rijsdijk FV, Dahl RE, McGuffin P, Eley TC. Associations between
sleep problems, anxiety and depression in twins at 8 years of age. Pediatrics
*18. Alfano CA, Ginsburg GS, Kingery JN. Sleep-related problems among chil-
dren and adolescents with anxiety disorders. J Am Acad Child Adolesc
19. Hudson JL,GradisarM,GambleA, SchnieringCA,RebeloI.The sleeppatterns
*20. Forbes EE, Bertocci MA, Gregory AM, Ryan ND, Axelson DA, Birmaher B,
et al. Objective sleep in pediatric anxiety disorders and major depressive
disorder. J Am Acad Child Adolesc Psychiatry 2008;47:148e55.
21. Rapoport J, Elkins R, Langer DH, Sceery W, Buchsbaum MS, Gillin JC, et al.
22. Gregory AM, Eley TC. Sleep problems, anxiety and cognitive style in school-
aged children. Infant Child Dev 2005;14:435e44.
23. Alfano CA, Beidel DC, Turner SM, Lewin DS. Preliminary evidence for sleep
complaints among children referred for anxiety. Sleep Med 2006;7:467e73.
24. Ivanenko A, Crabtree VM, Gozal D. Sleep and depression in children and
adolescents. Sleep Med Rev 2005;9:115e29.
25. Ryan ND, Puig-Antich J, Ambrosini P, Rabinovich H, Robinson D, Nelson B,
et al. The clinical picture of major depression in children and adolescents.
Arch Gen Psychiatry 1987;44:854e61.
26. Dahl RE, Puig-Antich J, Ryan ND, Nelson B, Dachille S, Cunningham SL, et al.
EEG sleep in adolescents with major depression e The role of suicidality
and inpatient status. J Affect Disord 1990;19:63e75.
27. Puig-Antich J, Goetz R, Hanlon C, Davies M, Thompson J, Chambers WJ, et al.
Sleep architecture and REM-sleep measures in prepubertal children with
major depression e A controlled study. Arch Gen Psychiatry 1982;39:932e9.
28. Arana-Lechuga Y, Nunez-Ortiz R, Teran-Perez G, Castillo-Montoya C,
Jimenez-Anguiano A, Gonzalez-Robles RO, et al. Sleep-EEG patterns of
school children suffering from symptoms of depression compared to
healthy controls. World J Biol Psychiatry 2008;9:115e20.
29. Dahl RE, Ryan ND, Birmaher B, AlShabbout M, Williamson DE, Neidig M,
et al. Electroencephalographic sleep measures in prepubertal depression.
Psychiatry Res 1991;38:201e14.
30. Emslie GJ, Rush AJ, Weinberg WA, Rintelmann JW, Roffwarg HP. Children
with major depression show reduced rapid eye-movement latencies. Arch
Gen Psychiatry 1990;47:119e24.
31. Lahmeyer HW, Poznanski EO, Bellur SN. EEG sleep in depressed adoles-
cents. Am J Psychiatry 1983;140:1150e3.
32. Alfano CA, Gamble AL. The role of sleep in childhood psychiatric disorders.
Child Youth Care Forum 2009;38:327e40.
33. Armitage R, Hoffmann R, Emslie G, Rintelman J, Moore J, Lewis K. Rest-
activity cycles in childhood and adolescent depression. J Am Acad Child
Adolesc Psychiatry 2004;43:761e9.
34. Lofthouse N, Gilchrist R, Splaingard M. Mood-related sleep problems in chil-
dren and adolescents. Child Adolesc Psychiatr Clin N Am 2009;18:893e916.
35. Owens JA. Sleep disorders and attention-deficit/hyperactivity disorder. Curr
Psychiatry Rep 2008;10:439e44.
36. Sadeh A, Pergamin L, Bar-Haim Y. Sleep in children with attention-deficit
hyperactivity disorder: a meta-analysis of polysomnographic studies. Sleep
Med Rev 2006;10:381e98.
37. Cortese S, Faraone SV, Konofal E, Lecendreux M. Sleep in children with
attention-deficit/hyperactivity disorder: meta-analysis of subjective and
objective studies. J Am Acad Child Adolesc Psychiatry 2009;48:894e908.
38. Walters AS, Silvestri R, Zucconi M, Chandrashekariah R, Konofal E. Review
of the possible relationship and hypothetical links between attention
deficit hyperactivity disorder (ADHD) and the simple sleep related move-
ment disorders, parasomnias, hypersomnias, and circadian rhythm disor-
ders. J Clin Sleep Med 2008;4:591e600.
39. Gruber R, Sadeh A. Sleep and neurobehavioral functioning in boys with
attention-deficit/hyperactivity disorder and no reported breathing prob-
lems. Sleep 2004;27:267e73.
*40. Owens J, Sangal RB, Sutton VK, Bakken R, Allen AJ, Kelsey D. Subjective and
objective measures of sleep in children with attention-deficit/hyperactivity
disorder. Sleep Med 2009;10:446e56.
41. Beebe DW, Gozal D. Obstructive sleep apnea and the prefrontal cortex:
towards a comprehensive model linking nocturnal upper airway obstruc-
tion to daytime cognitive and behavioral deficits. J Sleep Res 2002;11:1e16.
neuropsychological functioning in adolescence. Pediatrics 2009;123:1171e6.
43. Chervin RD, Dillon JE, Archbold KH, Ruzicka DL. Conduct problems and
symptoms of sleep disorders in children. J Am Acad Child Adolesc Psychiatry
*44. Goodnight JA, Bates JE, Staples AD, Pettit GS, Dodge KA. Temperamental
resistance to control increases the association between sleep problems and
externalizing behavior development. J Fam Psychol 2007;21:39e48.
45. Gregory AM, Van den Ende J, Willis TA, Verhulst FC. Parent-reported sleep
problems during development predicts self-reported anxiety/depression,
attention problems and aggression later in life. Arch Ped Adolesc Med
46. Aronen ET, Paavonen EJ, Fjallberg M, Soininen M, Torronen J. Sleep and
psychiatric symptoms in school-age children. J Am Acad Child Adolesc
To advance this important area of research, there is urgent
1) Use multi-methods (i.e., objective and subjective
measures) to assess sleep;
2) Measure sleep in large-scale longitudinal studies (e.g.,
epidemiological studies focusing on development);
3) Conduct controlled experiments to establish the effects
of sleep variations on emotional and behavioral
4) Take an interdisciplinary approach to further under-
stand the links between sleep and associated difficulties
(e.g., examining environmental risk factors for sleep
disturbance in a genetically sensitive twin design).
*The most important references are denoted by an asterisk.
A.M. Gregory, A. Sadeh / Sleep Medicine Reviews 16 (2012) 129e136
47. Sadeh A, Gruber R, Raviv A. Sleep, neurobehavioral functioning, and Download full-text
behavior problems in school-age children. Child Dev 2002;73:405e17.
48. Moore M, Kirchner HL, Drotar D, Johnson N, Rosen C, Ancoli-Israel S, et al.
Relationships among sleepiness, sleep time, and psychological functioning
in adolescents. J Pediatr Psych 2009;34:1175e83.
49. Wong MM, Brower KJ, Fitzgerald HE, Zucker RA. Sleep problems in early
childhood and early onset of alcohol and other drug use in adolescence.
Alcohol Clin Exp Res 2004;28:578e87.
50. Wong MM, Brower KJ, Zucker RA. Childhood sleep problems, early onset of
substance use and behavioral problems in adolescence. Sleep Med
51. Doo S, Wing YK. Sleep problems of children with pervasive developmental
disorders: correlation with parental
52. Goldman SE, Surdyka K, Cuevas R, Adkins K, Wang L, Malow BA. Defining the
sleep phenotype in children with autism. Dev Neuropsych 2009;34:560e73.
53. Richdale AL, Schreck KA. Sleep problems in autism spectrum disorders:
prevalence, nature, & possible biopsychosocial aetiologies. Sleep Med Rev
54. Mayes SD, Calhoun SL. Variables related to sleep problems in children with
autism. Res Autism Spectr Dis 2009;3:931e41.
55. Allik H, Larsson JO, Smedje H. Sleep patterns in school-age children with
Asperger syndrome or high-functioning autism: a follow-up study. J Autism
Dev Dis 2008;38:1625e33.
56. Wiggs L, Stores G. Sleep patterns and sleep disorders in children with
autistic spectrum disorders: insights using parent report and actigraphy.
Dev Med Child Neurol 2004;46:372e80.
57. Elia M, Ferri R, Musumeci SA, Del Gracco S, Bottitta M, Scuderi C, et al. Sleep
in subjects with autistic disorder: a neurophysiological and psychological
study. Brain Dev 2000;22:88e92.
*58. Miano S, Bruni V, Elia M, Trovato A, Smerieri A, Verrillo E, et al. Sleep in
children with autistic spectrum disorder: a questionnaire and poly-
somnographic study. Sleep Med 2007;9:64e70.
59. Kirov R, Kinkelbur J, Banaschewski T, Rothenberger A. Sleep patterns in
children with attention-deficit/hyperactivity disorder, tic disorder, and
comorbidity. J Child Psychol Psychiatry 2007;48:561e70.
60. Smedje H, Broman JE, Hetta J. Short-term prospective study of sleep
disturbances in 5e8-year-old children. Acta Paediatr 2001;90:1456e63.
61. Ong SH, Wickramaratne P, Tang M, Weissman MM. Early childhood sleep
and eating problems as predictors of adolescent and adult mood and
anxiety disorders. J Affect Disord 2006;96:1e8.
62. Roane BM, Taylor DJ. Adolescent insomnia as a risk factor for early adult
depression and substance abuse. Sleep 2008;31:1351e6.
63. Gregory AM, Caspi A, Eley TC, Moffitt TE, O’Connor TG, Poulton R.
Prospective longitudinal associations between persistent sleep problems in
childhood and anxiety and depression disorders in adulthood. J Abnorm
64. Roberts RE, Roberts CR, Chen IG. Impact of insomnia on future functioning
of adolescents. J Psychosom Res 2002;53:561e9.
65. Achenbach TM, Edelbrock C. Manual for the child behavior checklist and
revised child behavior profile. Burlington: Vermont; 1983.
66. Gregory AM, Rijsdijk FV, Lau JF, Dahl RE, Eley TC. The direction of longi-
tudinal associations between sleep problems and depression symptoms:
a study of twins aged 8 and 10 years. Sleep 2009;32:189e99.
*67. Johnson EO, Roth T, Breslau N. The association of insomnia with anxiety
disorders and depression: exploration of the direction of risk. J Psychiatr Res
evidence and taxonomic implications. J Abnorm Psychol 1991;100:316e36.
69. Bonnet MH, Arand DL. Hyperarousal and insomnia. Sleep Med Rev
70. Gauthier AK, Chevrette T, Bouvier H, Godbout R. Evening vs. morning wake
EEG activity in adolescents with anxiety disorders. J Anxiety Disord
*71. O’Callaghan FV, Al Mamun A, O’Callaghan M, Clavarino A, Williams GM,
Bor W, et al. The link between sleep problems in infancy and early child-
hood and attention problems at 5 and 14 years: evidence from a birth
cohort study. Early Hum Dev 2010;86:419e24.
72. Quach J, Hiscock H, Canterford L, Wake M. Outcomes of child sleep prob-
lems over the school-transition period: Australian population longitudinal
study. Pediatrics 2009;123:1287e92.
*73. El-Sheikh M, Kelly RJ, Buckhalt JA, Hinnant JB. Children’s sleep and
adjustment over time: the role of socioeconomic context. Child Dev
74. HarveyAG.Insomnia: symptom
75. Plomin R, DeFries JC, McClearn GE, McGuffin P. Behavioral genetics. 5th ed.
New York: Worth Publishers; 2008.
76. Van den Oord EJCG, Boomsma DI, Verhulst FC. A study of genetic and
environmental effects on the co-occurrence of problem behaviors in three-
year-old twins. J Abnorm Psychol 2000;109:360e72.
77. Heath AC, Eaves LJ, Kirk KM, Martin NG. Effects of lifestyle, personality,
symptoms of anxiety and depression, and genetic predisposition on
Dev Med ChildNeurol
Clin Psychol Rev
78. Kendler KS, Heath AC, Martin NG, Eaves LJ. Symptoms of anxiety and
depression: same genes, different environments? Arch Gen Psychiatry
79. Jones KHS, Ellis J, von Schantz M, Skene DJ, Dijk DJ, Archer SN. Age-related
change in the association between a polymorphism in the PER3 gene and
preferred timing of sleep and waking activities. J Sleep Res 2007;16:12e6.
80. Jouvet M. Biogenic amines and states of sleep. Science 1969;163:32e41.
81. Lesch KP, Bengel D, Heils A, Zhang Sabol S, Greenburg BD, Petri S, et al.
Association of anxiety-related traits with a polymorphism in the serotonin
transporter gene regulatory region. Science 1996;274:1527e31.
82. Alia-Klein N, Goldstein RZ, Kriplani A, Logan J, Tomasi D, Williams B, et al.
Brain monoamine oxidase A activity predicts trait aggression. J Neurosci
83. Brummett BH, Krystal AD, Siegler IC, Kuhn C, Surwit RS, Zuchner S, et al.
Associations of a regulatory polymorphism of monoamine oxidase-A gene
promoter (MAOA-uVNTR) with symptoms of depression and sleep quality.
Psychosom Med 2007;69:396e401.
84. Gruber R, Grizenko N, Schwartz G, Ben Amor L, Gauthier J, de Guzman R,
et al. Sleep and COMT polymorphism in ADHD children: preliminary
actigraphic data. J Am Acad Child Adolesc Psychiatry 2006;45:982e9.
85. Gregory AM, Eley TC, O’Connor TG, Rijsdijk FV, Plomin R. Family influences
on the association between sleep problems and anxiety in a large sample of
pre-school aged twins. Person Ind Diff 2005;39:1337e48.
86. Williams K, Chambers M, Logan S, Robinson D. Association of common
health symptoms with bullying in primary school children. Br Med J
87. Buckhalt JA, El-Sheikh M, Keller P. Children’s sleep and cognitive func-
tioning: race and socioeconomic status as moderators of effects. Child Dev
88. Miech RA, Caspi A, Moffitt TE, Wright BRE, Silva PA. Low socioeconomic
status and mental disorders: a longitudinal study of selection and causa-
tion during young adulthood. Am J Sociol 1999;104:1096e131.
89. Bell BG, Belsky J. Parents, parenting, and children’s sleep problems:
exploring reciprocal effects. Br J Dev Psych 2008;26:579e93.
90. Sadeh A, Tikotzky L, Scher A. Parenting and infant sleep. Sleep Med Rev
91. Cousins JC, Bootzin RR, Stevens SJ, Ruiz BS, Haynes PL. Parental involve-
ment, psychological distress, and sleep: a preliminary examination in
sleep-disturbed adolescents with a history of substance abuse. J Fam Psych
92. Adam EK, Snell EK, Pendry P. Sleep timing and quantity in ecological and
family context: a nationally representative time-diary study. J Fam Psych
93. Dahl RE, El-Sheikh M. Considering sleep in a family context: introduction to
the special issue. J Fam Psych 2007;21:1e3.
94. Charuvastra A, Cloitre M. Safe enough to sleep: sleep disruptions associated
with trauma, posttraumatic stress, and anxiety in children and adolescents.
Child Adolesc Psychiatr Clin N Am 2009;18:877e91.
95. Sadeh A. Stress, trauma, and sleep in children. Child Adolesc Psychiatr Clin N
96. Brummett BH, Krystal AD, Ashley-Koch A, Kuhn CM, Zuchner S, Siegler IC,
et al. Sleep quality varies as a function of 5-HTTLPR genotype and stress.
Psychosom Med 2007;69:621e4.
97. Moffitt TE, Caspi A, Rutter M. Strategy for investigating interactions
between measured genes and measured environments. Arch Gen Psychiatry
98. van der Heijden KB, Smits MG, van Someren EJW, Gunning WB. Idiopathic
chronic sleep onset insomnia in attention-deficit/hyperactivity disorder:
a circadian rhythm sleep disorder. Chronobiol Int 2005;22:559e70.
99. Melke J, Botros HG, Chaste P, Betancur C, Nygren G, Anckarsater H, et al.
Abnormal melatonin synthesis in autism spectrum disorders. Mol Psychi-
*100. van der Heijden KB, Smits MG, van Someren EJW, Ridderinkhof KR,
Gunning WB. Effect of melatonin on sleep, behavior, and cognition in ADHD
and chronic sleep-onset insomnia. J Am Acad Child Adolesc Psychiatry
101. Paavonen EJ, Nieminen-von Wendt T, Vanhala R, Aronen ET, von Wendt L.
Effectiveness of melatonin in the treatment of sleep disturbances in children
with Asperger disorder. J Child Adolesc Psychopharmacol 2003;13:83e95.
102. Sadeh A, Klitzke M, Anders TF, Acebo C. Sleep and aggressive-behavior in
a blind, retarded adolescent e A concomitant schedule disorder e case-
study. J Am Acad Child Adolesc Psychiatry 1995;34:820e4.
103. Richardson GS. Human physiological models of insomnia. Sleep Med
*104. Walker MP, van der Helm E. Overnight therapy? The role of sleep in
emotional brain processing. Psychol Bull 2009;135:731e48.
105. Yoo SS, Gujar N, Hu P, Jolesz FA, Walker MP. The human emotional brain
106. van der Helm E, Gujar N, Walker MP. Sleep deprivation impairs the accurate
recognition of human emotions. Sleep 2010;33:335e42.
A.M. Gregory, A. Sadeh / Sleep Medicine Reviews 16 (2012) 129e136