Evaluating alternative models of youth externalizing using quantitative genetic analyses

Interest has increased in the recent literature on characterizing psychopathology dimensionally in hierarchical models. One dimension of psychopathology that has received considerable attention is externalizing. Although extensively studied and well-characterized in late adolescents and adults, delineation of the externalizing spectrum in youth has lagged behind. As a complement to structural analyses of externalizing, in this study, we use quantitative genetic analyses of twin data to adjudicate among alternative models of youth externalizing that differ in granularity. Specifically, we compared model fit, estimates of genetic and environmental influences on the externalizing dimension, and the average, variability, and precision of genetic and environmental influences on individual symptoms due to the externalizing dimension, specific symptom dimensions, and unique etiological influences. Given that none of these criteria are definitive on their own, we looked to the confluence of these criteria to exclude particular models while highlighting others as leading contenders. We analyzed parent-report data on 38 externalizing symptoms from a population-representative, ethnically diverse sample of 883 youth twin pairs (51% female), who were on average 8.5 years old. Although models including an externalizing composite and attention deficit hyperactivity disorder, oppositional defiant disorder, and conduct disorder diagnoses and symptom dimensions showed similar heritability to latent variable models of externalizing, models that included latent dimensions of externalizing and more fine-grained symptom dimensions fit better and were more balanced in the magnitude of genetic and environmental influences on individual symptoms due to the externalizing dimension and specific symptom dimensions. Pending replication, these more granular and elaborated model(s) can be useful for advancing research on causes and outcomes of youth externalizing and its fine-grained specific components. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

The p factor of psychopathology and personality in middle childhood: genetic and gestational risk factors

BACKGROUND

A joint, hierarchical structure of psychopathology and personality has been reported in adults but should also be investigated at earlier ages, as psychopathology often develops before adulthood. Here, we investigate the joint factor structure of psychopathology and personality in eight-year-old children, estimate factor heritability and explore external validity through associations with established developmental risk factors.

METHODS

Phenotypic and biometric exploratory factor analyses with bifactor rotation on genetically informative data from the Norwegian Mother, Father, and Child Cohort (MoBa) study. The analytic sub-sample comprised 10 739 children (49% girls). Mothers reported their children's symptoms of depression (Short Moods and Feelings Questionnaire), anxiety (Screen for Anxiety Related Disorders), attention-deficit/hyperactivity disorder inattention and hyperactivity, oppositional-defiant disorder, conduct disorder (Parent/Teacher Rating Scale for Disruptive Behavior Disorders), and Big Five personality (short Hierarchical Personality Inventory for Children). Developmental risk factors (early gestational age and being small for gestational age) were collected from the Medical Birth Registry.

RESULTS

Goodness-of-fit indices favored a p factor model with three residual latent factors interpreted as negative affectivity, positive affectivity, and antagonism, whereas psychometric indices favored a one-factor model. ADE solutions fitted best, and regression analyses indicated a negative association between gestational age and the p factor, for both the one- and four-factor solutions.

CONCLUSION

Correlations between normative and pathological traits in middle childhood mostly reflect one heritable and psychometrically interpretable p factor, although optimal fit to data required less interpretable residual latent factors. The association between the p factor and low gestational age warrants further study of early developmental mechanisms.

The Behavioral Phenotype of 7q11.23 Duplication Syndrome Includes Risk for Oppositional Behavior and Aggression

OBJECTIVE

7q11.23 duplication syndrome (Dup7) is a genetic disorder with a variable phenotype associated with cognitive and behavioral characteristics including a high incidence of expressive language difficulties, social anxiety, and oppositional or disruptive behavior. Correlates of aggression and oppositionality were examined.

METHOD

Participants were 63 children with genetically confirmed Dup7 between the ages of 4 and 17 years. A multimethod, multi-informant approach was used to assess aggression and oppositional behavior, and the contributions of cognitive functioning, expressive language, autism spectrum, social anxiety, and hyperactivity/impulsivity (H/I) symptomatology were considered.

RESULTS

Elevated levels of aggression and oppositional behavior were found. Cognitive functioning, expressive language, and autism spectrum disorder symptomatology were not significantly related to parent ratings of aggression, although young children who had language and nonverbal cognitive delays were most likely to demonstrate examiner-observed aggression. Social anxiety and H/I symptomatology were related to defiant/aggressive and oppositional behavior.

CONCLUSION

Genes in the 7q11.23 region duplicated in Dup7, in transaction with the environment, may contribute to aggressive and oppositional behavior.

A Methylome-Wide Association Study of Trajectories of Oppositional Defiant Behaviors and Biological Overlap With Attention Deficit Hyperactivity Disorder

In 671 mother-child (49% male) pairs from an epidemiological birth cohort, we investigated (a) prospective associations between DNA methylation (at birth) and trajectories (ages 7-13) of oppositional defiant disorder (ODD), and the ODD subdimensions of irritable and headstrong; (b) common biological pathways, indexed by DNA methylation, between ODD trajectories and attention deficit hyperactivity disorder (ADHD); (c) genetic influence on DNA methylation; and (d) prenatal risk exposure associations. Methylome-wide significant associations were identified for the ODD and headstrong, but not for irritable. Overlap analysis indicated biological correlates between ODD, headstrong, and ADHD. DNA methylation in ODD and headstrong was (to a degree) genetically influenced. DNA methylation associated with prenatal risk exposures of maternal anxiety (headstrong) and cigarette smoking (ODD and headstrong).

Parental involvement as an etiological moderator of middle childhood oppositional defiant disorder

The goal of this study was to investigate parental involvement as an etiologic moderator of oppositional defiant disorder (ODD) during middle childhood. Previous studies examining the influence of genetic and environmental factors on ODD have not considered whether and how these factors might vary by parental involvement. We thus conducted a series of "latent genetic by measured environmental" interaction analyses, in which measured parental involvement was allowed to moderate genetic, shared, and nonshared environmental influences on child ODD. Participants include 1,027 twin pairs (age ranged from 6 to 11 years old) from the Michigan State University Twin Registry. Results did indeed suggest that the etiology of ODD varies with maternal involvement, such that genetic influence on ODD became more prominent as maternal involvement decreased. However, these results were specific to children's perceptions of maternal involvement and did not extend to maternal perceptions of her involvement. There was no evidence that paternal involvement moderated the etiology of ODD, regardless of informant. The different results found in twins' and parents' data are consistent with those in previous research showing that children may have different perceptions from parents' about their family relationships and that this discrepancy needs to be taken into account in future research. (PsycINFO Database Record

Trait Impulsivity and the Externalizing Spectrum

This article reviews evidence that trait impulsivity-expressed early in life as the hyperactive-impulsive and combined presentations of attention-deficit/hyperactivity disorder (ADHD)-is a bottom-up, subcortically mediated vulnerability to all externalizing disorders. This vulnerability arises from deficient mesolimbic dopamine responding, which imbues psychological states (irritability, discontentment) that motivate excessive approach behavior (hyperactivity, impulsivity). Through complex interactions with (a) aversive motivational states that arise from largely independent subcortical systems, (b) emotion regulatory mechanisms that arise from top-down, cortical modulation of subcortical neural function, and (c) environmental risk factors that shape and maintain emotion dysregulation, trait impulsivity confers vulnerability to increasingly severe externalizing behaviors across development. This perspective highlights the importance of identifying transdiagnostic neural vulnerabilities to psychopathology; dovetails with the hierarchical, latent structure of psychopathology; and suggests that progression along the externalizing spectrum is an ontogenic process whereby a common, multifactorially inherited trait interacts with endogenous and exogenous influences to yield increasingly intractable externalizing behaviors across development.

Chronic Stressors and Adolescents' Externalizing Problems: Genetic Moderation by Dopamine Receptor D4. The TRAILS Study

The existing literature does not provide consistent evidence that carriers of the Dopamine D4 Receptor 7-repeat allele are more sensitive to adverse environmental influences, resulting in enhanced externalizing problems, compared to noncarriers. One explanation is that the adverse influences examined in prior studies were not severe, chronic, or distressing enough to reveal individual differences in sensitivity reflected by DRD4–7R. This study examined whether the 7-repeat allele moderated the association between chronic stressors capturing multiple stressful aspects of individuals’ lives and externalizing problems in adolescence. We expected that chronic stressor levels would be associated with externalizing levels only in 7-repeat carriers. Using Linear Mixed Models, we analyzed data from 1621 Dutch adolescents (52.2% boys), obtained in three measurement waves (mean age approximately 11, 13.5, and 16 years) from the TRacking Adolescents’ Individual Lives Survey (TRAILS) population-based birth cohort and the parallel clinic-referred cohort. Across informants, we found that higher levels of chronic stressors were related to higher externalizing levels in 7-repeat carriers but not in noncarriers, as hypothesized. Although previous studies on the 7-repeat allele as a moderator of environmental influences on adolescents’ externalizing problems have not convincingly demonstrated individual differences in sensitivity to adverse environmental influences, our findings suggest that adolescent carriers of the Dopamine D4 Receptor 7-repeat allele are more sensitive to chronic, multi-context stressors than noncarriers.

Oxytocin and vasopressin hormone genes in children's externalizing problems: A cognitive endophenotype approach

Externalizing problems are among the most common mental health problems of children. Research suggests that these problems are heritable, yet little is known about the specific genes involved in their pathophysiology. The current study examined a genotype-endophenotype-phenotype model of externalizing problems in 320 preschool-aged children. Markers of the oxytocin (OXT) and arginine vasopressin (AVP) hormone genes were selected as candidates owing to their known association with psychopathology in other domains. We tested whether OXT and AVP variants were related to children's externalizing problems, as well as two cognitive endophenotypes presumed to underlie these problems: theory of mind (ToM) and executive functioning (EF). Externalizing problems were assessed at age 4.5 using a previously-validated rating scale. ToM and EF were measured with age-appropriate tasks. Using a family-based association design and controlling for non-genomic confounds, support was found for an association between a two-marker OXT haplotype (rs2740210-rs2770378) and a two-marker AVP haplotype (rs1887854-rs3761249) and externalizing problems. Specific associations of these haplotypes with ToM and EF were also observed. Further, ToM and EF were shown to independently and jointly predict externalizing problems, and to partially mediate the effects of OXT and AVP on externalizing problems. This study provides the first evidence that genetic variation in OXT and AVP may contribute to individual differences in childhood externalizing problems, and that these effects may operate through emerging neurocognitive abilities in the preschool period.

Maternal pre-pregnancy weight and externalising behaviour problems in preschool children: a UK-based twin study

OBJECTIVE

To estimate the heritability of child behaviour problems and investigate the association between maternal pre-pregnancy overweight and child behaviour problems in a genetically sensitive design.

DESIGN

Observational cross-sectional study.

SETTING

The Twins and Multiple Births Association Heritability Study (TAMBAHS) is an online UK-wide volunteer-based study investigating the development of twins from birth until 5 years of age.

PARTICIPANTS

A total of 443 (16% of the initial registered members) mothers answered questions on pre-pregnancy weight and their twins' internalising and externalising problems using the Child Behavior Checklist and correcting for important covariates including gestational age, twins' birth weight, age and sex, mother's educational level and smoking (before, during and after pregnancy).

PRIMARY OUTCOMES

The heritability of behaviour problems and their association with maternal pre-pregnancy weight.

RESULTS

The genetic analysis suggested that genetic and common environmental factors account for most of the variation in externalising disorders (an ACE model was the most parsimonious with genetic factors (A) explaining 46% (95% CI 33% to 60%) of the variance, common environment (C) explaining 42% (95% CI 27% to 54%) and non-shared environmental factors (E) explaining 13% (95% CI 10% to 16%) of the variance. For internalising problems, a CE model was the most parsimonious model with the common environment explaining 51% (95% CI 44% to 58%) of the variance and non-shared environment explaining 49% (95% CI 42% to 56%) of the variance. Moreover, the regression analysis results suggested that children of overweight mothers showed a trend (OR=1.10, 95% CI 0.58% to 2.06) towards being more aggressive and exhibit externalising behaviours compared to children of normal weight mothers.

CONCLUSIONS

Maternal pre-pregnancy weight may play a role in children's aggressive behaviour.

DSM-IV defined conduct disorder and oppositional defiant disorder: an investigation of shared liability in female twins

BACKGROUND

DSM-IV specifies a hierarchal diagnostic structure such that an oppositional defiant disorder (ODD) diagnosis is applied only if criteria are not met for conduct disorder (CD). Genetic studies of ODD and CD support a combination of shared genetic and environmental influences but largely ignore the imposed diagnostic structure.

METHOD

We examined whether ODD and CD share an underlying etiology while accounting for DSM-IV diagnostic specifications. Data from 1446 female twin pairs, aged 11-19 years, were fitted to two-stage models adhering to the DSM-IV diagnostic hierarchy.

RESULTS

The models suggested that DSM-IV ODD-CD covariation is attributed largely to shared genetic influences.

CONCLUSIONS

This is the first study, to our knowledge, to examine genetic and environmental overlap among these disorders while maintaining a DSM-IV hierarchical structure. The findings reflect primarily shared genetic influences and specific (i.e. uncorrelated) shared/familial environmental effects on these DSM-IV-defined behaviors. These results have implications for how best to define CD and ODD for future genetically informed analyses.

Understanding the relative contributions of direct environmental effects and passive genotype-environment correlations in the association between familial risk factors and child disruptive behavior disorders

BACKGROUND

Previous work reports an association between familial risk factors stemming from parental characteristics and offspring disruptive behavior disorders (DBDs). This association may reflect (a) the direct effects of familial environment and (b) a passive gene-environment correlation (r(GE)), wherein the parents provide both the genes and the environment. The current study examined the contributions of direct environmental influences and passive r(GE) by comparing the effects of familial risk factors on child DBDs in genetically related (biological) and non-related (adoptive) families.

METHOD

Participants were 402 adoptive and 204 biological families. Familial environment was defined as maternal and paternal maladaptive parenting and antisociality, marital conflict and divorce; offspring DBDs included attention deficit hyperactivity disorder (ADHD), conduct disorder (CD) and oppositional defiant disorder (ODD). Mixed-level regressions estimated the main effects of familial environment, adoption status and the familial environment by adoption status interaction term, which tested for the presence of passive r(GE).

RESULTS

There was a main effect of maternal and paternal maladaptive parenting and marital discord on child DBDs, indicating a direct environmental effect. There was no direct environmental effect of maternal or paternal antisociality, but maternal and paternal antisociality had stronger associations with child DBDs in biological families than adoptive families, indicating the presence of a passive r(GE).

CONCLUSIONS

Many familial risk factors affected children equally across genetically related and non-related families, providing evidence for direct environmental effects. The relationship of parental antisociality and offspring DBDs was best explained by a passive r(GE), where a general vulnerability toward externalizing psychopathology is passed down by the parents to the children.

How and why does the 5-HTTLPR gene moderate associations between maternal unresponsiveness and children's disruptive problems?

This study tested the 5-HTTLPR gene as a moderator in the relation between maternal unresponsiveness and child externalizing symptoms in a disadvantaged, predominantly Black sample of two hundred and one 2-year-old children and their mothers. Using a multimethod, prospective design, structural equation model analyses indicated that maternal unresponsiveness significantly predicted increases in externalizing symptoms 2 years later only for children possessing the LL genotype. Moderation was expressed in a "for better" or "for worse" form hypothesized in differential susceptibility theory. In examining why the risk posed by maternal unresponsiveness differed across the 5-HTTLPR polymorphism, mediated moderation analyses showed that children's angry reactivity to maternal negativity partly accounted for the greater susceptibility of homozygous L carriers to variations in maternal unresponsiveness.

Personality dimensions as common and broadband-specific features for internalizing and externalizing disorders

Several researchers have suggested that the nature of the covariation between internalizing and externalizing disorders may be understood better by examining the associations between temperament or personality and these disorders. The present study examined neuroticism as a potential common feature underlying both internalizing and externalizing disorders and novelty seeking as a potential broad-band specific feature influencing externalizing disorders alone. Participants were 12- to 18-year-old twin pairs (635 monozygotic twin pairs and 691 dizygotic twin pairs; 48 % male and 52 % female) recruited from the Colorado Center for Antisocial Drug Dependence. Genetic and nonshared environmental influences shared in common with neuroticism influenced the covariation among distinct internalizing disorders, the covariation among distinct externalizing disorders, and the covariation between internalizing and externalizing disorders. Genetic influences shared in common with novelty seeking influenced the covariation among externalizing disorders and the covariation between major depressive disorder and externalizing disorders, but not the covariation among internalizing disorders or between anxiety disorders and externalizing disorders. Also, after accounting for genetic and environmental influences shared in common with neuroticism and novelty seeking, there were no significant common genetic or environmental influences among the disorders examined, suggesting that the covariance among the disorders is sufficiently explained by neuroticism and novelty seeking. We conclude that neuroticism is a heritable common feature of both internalizing disorders and externalizing disorders, and that novelty seeking is a heritable broad-band specific factor that distinguishes anxiety disorders from externalizing disorders.

Managing disruptive behaviour disorders in children

The age at which individuals are most physically aggressive is 22 months. However, some children fail to inhibit this normal aggression and by the time they are three or four are showing signs of oppositional defiant disorder. In older children persistent antisocial behaviour is classified as conduct disorder. At any age, antisocial behaviour is on a continuum, and while the most severe 5% or so will meet diagnostic criteria, those falling short are often described as having conduct problems. Epidemiological follow-up surveys show that the risk of poor outcomes in antisocial children is very high. The causes are multiple but two sets of factors stand out. First, genetic predisposition. Even children adopted away from violent or criminal parents have three or four times the rate of antisocial behaviour and second, poor parenting. Watching and waiting is a reasonable strategy if the antisocial behaviour is not very severe. It is important to be vigilant for severe tantrums or aggression occurring almost every day, harsh, rough, or inconsistent parenting and coexistent ADHD. If severity is moderate, referral to an evidence-based parenting group would be a good first move. If this fails to make things better, or if the child or parent has a comorbid condition, referral to CAMHS is indicated. For older children, aged 10 to 17, there are effective interventions such as anger management CBT and parenting groups for adolescents.

Separating the domains of oppositional behavior: comparing latent models of the conners' oppositional subscale

OBJECTIVE

Although oppositional defiant disorder (ODD) is usually considered the mildest of the disruptive behavior disorders, it is a key factor in predicting young adult anxiety and depression and is distinguishable from normal childhood behavior. In an effort to understand possible subsets of oppositional defiant behavior (ODB) that may differentially predict outcome, we used latent class analysis of mother report on the Conners' Parent Rating Scales Revised Short Forms (CPRS-R:S).

METHOD

Data were obtained from mother report for Dutch twins (7 years old, n = 7,597; 10 years old, n = 6,548; and 12 years old, n = 5,717) from the Netherlands Twin Registry. Samples partially overlapped at ages 7 and 10 years (19% overlapping) and at ages 10 and 12 years (30% overlapping), but not at ages 7 and 12 years. Oppositional defiant behavior was measured using the six-item Oppositional subscale of the CPRS-R:S. Multilevel LCA with robust standard error estimates was performed using the Latent Gold program to control for twin-twin dependence in the data. Class assignment across ages was determined and an estimate of heritability for each class was calculated. Comparisons with maternal report Child Behavior Checklist (CBCL) scores were examined using linear mixed models at each age, corrected for multiple comparisons.

RESULTS

The LCA identified an optimal solution of four classes across age groups. Class 1 was associated with no or low symptom endorsement (69-75% of the children); class 2 was characterized by defiance (11-12%); class 3 was characterized by irritability (9-11%); and class 4 was associated with elevated scores on all symptoms (5-8%). Odds ratios for twins being in the same class at each successive age point were higher within classes across ages than between classes. Heritability within the two "intermediate" classes was nearly as high as for the class with all symptoms, except for boys at age 12. Children in the Irritable class were more likely to have mood symptoms on the CBCL scales than children in the Defiant class but demonstrated similar scores on aggression and externalizing scales. Children in the All Symptoms class were higher in both internalizing and externalizing scales and subscales.

CONCLUSIONS

The LCA indicates four distinct latent classes of oppositional defiant behavior, in which the distinguishing feature between the two intermediate classes (classes 2 and 3) is the level of irritability and defiance. Implications for the longitudinal course of these symptoms, association with other disorders, and genetics are discussed.

Gene-by-preschool interaction on the development of early externalizing problems

BACKGROUND

Preschool involves an array of new social experiences that may impact the development of early externalizing behavior problems over the transition to grade school.

METHODS

Using longitudinal data from a nationally representative sample of over 600 pairs of US twins, we tested whether the genetic and environmental influences on externalizing problems differed between children who did versus did not attend preschool.

RESULTS

At age 4, the genetic and environmental etiology of externalizing did not differ by preschool attendance. In contrast, by age 5 years (kindergarten age), the genetic and environmental etiology of externalizing significantly differed by preschool attendance. Among children who did not attend preschool, externalizing at age 5 was predominantly due to environmental influences (52% shared environment, 34% non-shared environment) rather than genetic differences (13%), whereas among children who had attended preschool, externalizing at age 5 was primarily due to genes (67%), and shared environmental influences were negligible (0%). These interactions represented the differential longitudinal persistence of genes and environments that contributed to externalizing at age 4. Sensitivity analyses ruled out confounding due to early mental ability, socioeconomic status, minority status, child age, and prior history of childcare.

CONCLUSIONS

These results indicate that preschool enrollment is associated with increased genetic and decreased shared environmental influences on the development of early externalizing behavior problems.

Annual research review: phenotypic and causal structure of conduct disorder in the broader context of prevalent forms of psychopathology

BACKGROUND

A better understanding of the nature and etiology of conduct disorder (CD) can inform nosology and vice versa. We posit that any prevalent form of psychopathology, including CD, can be best understood if it is studied in the context of other correlated forms of child and adolescent psychopathology using formal models to guide inquiry.

METHODS

Review of both cross-sectional and longitudinal studies of the place of CD in the phenotypic and causal structure of prevalent psychopathology, with an emphasis on similarities and differences between CD and oppositional defiant disorder (ODD). Papers were located using Web of Science by topic searches with no restriction on year of publication.

RESULTS

Although some important nosologic questions remain unanswered, the dimensional phenotype of CD is well defined. CD differs from other disorders in its correlates, associated impairment, and course. Nonetheless, it is robustly correlated with many other prevalent dimensions of psychopathology both concurrently and predictively, including both other 'externalizing' disorders and some 'internalizing' disorders. Based on emerging evidence, we hypothesize that these concurrent and predictive correlations result primarily from widespread genetic pleiotropy, with some genetic factors nonspecifically influencing risk for multiple correlated dimensions of psychopathology. In contrast, environmental influences mostly act to differentiate dimensions of psychopathology from one another both concurrently and over time. CD and ODD share half of their genetic influences, but their genetic etiologies are distinct in other ways. Unlike most other dimensions of psychopathology, half of the genetic influences on CD appear to be unique to CD. In contrast, ODD broadly shares nearly all of its genetic influences with other disorders and has little unique genetic variance.

CONCLUSIONS

Conduct disorder is a relatively distinct syndrome at both phenotypic and etiologic levels, but much is revealed by studying CD in the context of its causal and phenotypic associations with other disorders over time. Advancing and refining formal causal models that specify the common and unique causes and biological mechanisms underlying each correlated dimension of psychopathology should facilitate research on the fundamental nature and nosology of CD.

Attenuation of age-related changes in FOXO3a activity and the PI3K/Akt pathway by short-term feeding of ferulate

Ferulate (4-hydroxy-3-methoxycinnamic acid) is a well-known phenolic compound that scavenges free radicals and exerts anti-inflammatory effects. Forkhead box O3a (FOXO3a), a transcription factor that plays important roles in aging processes, decreases with age and is negatively regulated through phosphorylation by phosphatidylinositol 3-kinase (PI3K)/Akt signaling. The present study investigated the efficacy of short-term ferulate feeding on age-related changes in PI3K/Akt/FOXO3a and upstream insulin signaling pathways in aged rats. In addition, changes in manganese superoxide dismutase (MnSOD) and catalase expression were examined because of their dependence on PI3K/Akt/FOXO3a activity. Short-term feeding experiments were done with a diet containing ferulate that was given to aged rats at doses of 3 or 6 mg kg(-1) day(-1) for 10 days. Results showed that FOXO3a activity was increased in the ferulate-fed old group compared with the control old group. Also, ferulate suppressed the PI3K/Akt signaling pathway that is responsible for FOXO3a inhibition in aged rats. Plasma insulin levels and the upstream insulin signaling pathway were also modulated by ferulate correspondingly with PI3K/Akt/FOXO3a activity. The age-related decrease in two major antioxidant enzymes, MnSOD and catalase, was blunted by ferulate, which was accompanied by FOXO3a transcriptional activity. The significance of the present study is the finding that short-term feeding of ferulate effectively modulates age-related renal FOXO3a, PI3K/Akt and insulin signaling pathways, and MnSOD and catalase expression, all of which may be beneficial for attenuating the aging process.

Prevalence of the ADHD phenotype in 7- to 9-year-old children: effects of informant, gender and non-participation

PURPOSE

To estimate the prevalence of the ADHD phenotype based on parent and teacher reports in a general population sample of 7- to 9-year-old Norwegian children and evaluate the effect of parent attrition, gender and informant on the prevalence estimate.

METHODS

The population consisted of all children (N = 9,430) attending 2nd-4th grade in the City of Bergen, Norway. The 18 symptoms of ADHD corresponding to the SNAP-IV and DSM-IV were included in the Bergen Child Study questionnaire to teachers and parents. Teacher information was available for 9,137 children (97%) and information from both informants was available for the 6,237 children (66%) whose parents agreed to participate in the study.

RESULTS

The prevalence of the ADHD phenotype based on the combination of parent and teacher reports was 5.2% among participants. Teacher ratings of non-participants had a doubled rate of ADHD high scorers with an OR of 2.1 (95% CI, 1.9-2.4). The non-participant ADHD high scorers had more inattentive and fewer hyperactive/impulsive symptoms as compared to participating ADHD high scorers. Teachers reported high scores of hyperactivity/impulsivity and the combined symptom constellation much more frequently in boys than girls, while the difference between genders was less marked according to parent reports.

CONCLUSIONS

The ADHD phenotype was twice as prevalent among non-participants as among participants. Reported prevalences in population studies are therefore likely to be underestimates, if such attrition bias is not accounted for. Choice of informant, criteria for symptom count, definitions of subtypes and gender differences influence the prevalence estimates of the ADHD phenotype.

Higher-order genetic and environmental structure of prevalent forms of child and adolescent psychopathology

CONTEXT

It is necessary to understand the etiologic structure of child and adolescent psychopathology to advance theory and guide future research.

OBJECTIVE

To test alternative models of the higher-order structure of etiologic effects on 11 dimensions of child and adolescent psychopathology using confirmatory factor analyses of genetic and environmental covariances.

DESIGN

Representative sample of twins.

SETTING

Home interviews.

PARTICIPANTS

A total of 1571 pairs of 9- to 17-year-old twins.

MAIN OUTCOME MEASURES

Structured assessments of psychopathology using adult caregivers and youth as informants.

RESULTS

The best-fitting genetic model revealed that most genetic factors nonspecifically influence risk for either all 11 symptom dimensions or for dimensions of psychopathology within 1 of 2 broad domains. With some notable exceptions, dimension-specific genetic influences accounted for modest amounts of variance.

CONCLUSIONS

To inform theory and guide molecular genetic studies, an etiologic model is offered in which 3 patterns of pleiotropy are hypothesized to be the principal modes of genetic risk transmission for common forms of child and adolescent psychopathology. Some common environmental influences were found, but consistent with a "generalist genes, specialist environments" model, there was little sharing of environmental influences. This implies that prevalent dimensions of child and adolescent psychopathology mostly share their genetic liabilities but are differentiated by nonshared experiences.

A family based association study of DRD4, DAT1, and 5HTT and continuous traits of attention-deficit hyperactivity disorder

Despite its high heritability, genetic association studies of attention deficit-hyperactivity disorder (ADHD) have often resulted in somewhat small, inconsistent effects. Refining the ADHD phenotype beyond a dichotomous diagnosis and testing associations with continuous information from the underlying symptom dimensions may result in more consistent genetic findings. This study further examined the association between ADHD and the DRD4, DAT1, and 5HTT genes by testing their association with multivariate phenotypes derived from continuous measures of ADHD symptom severity. DNA was collected in 202 families consisting of at least one ADHD proband and at least one parent or sibling. VNTR polymorphisms of the DRD4 and DAT1 genes were significantly associated with the continuous ADHD phenotype. The association with DRD4 was driven by both inattentive and hyperactive symptoms, while the association with DAT1 was driven primarily by inattentive symptoms. These results use novel methods to build upon important connections between dopamine genes and their final behavioral manifestation as symptoms of ADHD.

The etiology of associations between negative emotionality and childhood externalizing disorders

Despite consistent documentation of associations between childhood negative emotionality and externalizing psychopathology, few genetically informative studies have investigated the etiology of that association. The goal of the current study was to delineate the etiology of the covariation of negative emotionality and childhood externalizing problems (e.g., oppositional defiant disorder, conduct disorder, inattention, and hyperactivity/impulsivity). Twin families were recruited from Georgia state birth records and completed parental report questionnaires of negative emotionality and common Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; American Psychiatric Association, 2000) child psychiatric disorders. Results suggest both genetic and environmental influences underlying negative emotionality and each externalizing symptom dimension, with additional evidence for sibling competition/rater contrast effects for inattention and hyperactivity/impulsivity. Bivariate model-fitting analyses indicated that a portion of the additive (43%-75%) and nonadditive (26%-100%) genetic influences underlying each symptom dimension was accounted for by the genetic influences underlying negative emotionality. Finally, an independent pathways model examining the etiology of the association between negative emotionality and the externalizing dimensions indicated that a substantial portion of the additive genetic, nonadditive genetic, and nonshared environmental influences underlying externalizing behavior is shared with negative emotionality.

A common genetic factor explains the covariation among ADHD ODD and CD symptoms in 9-10 year old boys and girls

Previous studies examining the covariation among Attention Deficit Hyperactivity Disorder (ADHD), Oppositional Defiant Disorder (ODD) and Conduct Disorder (CD) have yielded inconsistent results. Some studies have concluded that the covariation among these symptoms is due to common genetic influences, whereas others have found a common environmental overlap. The present study investigated the genetic and environmental correlations among these three childhood disorders, based on a sample of 1,219 twins, age 9-10 years. A latent externalizing behavior factor was found to explain the covariance among ADHD, ODD and CD symptoms. Genetic influences explained more than half of the variance in this externalizing factor in both boys and girls. There were also unique genetic and environmental influences in each set of symptoms, suggesting some etiological independence of the three disorders. Our findings have implications for molecular genetic studies trying to identify susceptibility genes for these disorders.

The Child Behavior Checklist-Pediatric Bipolar Disorder profile predicts a subsequent diagnosis of bipolar disorder and associated impairments in ADHD youth growing up: a longitudinal analysis

OBJECTIVE

To examine the predictive utility of the Child Behavior Checklist-Pediatric Bipolar Disorder (CBCL-PBD) profile to help identify children at risk for bipolar disorder.

METHOD

Subjects were ascertained from 2 identically designed longitudinal case-control family studies of subjects (males and females aged 6-18 years) with DSM-III-R attention-deficit/hyperactivity disorder (ADHD). Based on data from the baseline assessment, ADHD subjects without a lifetime diagnosis of bipolar disorder were stratified by the presence (CBCL-PBD positive, N=28) or absence (CBCL-PBD negative, N=176) of a CBCL-PBD score > or = 210 (total of attention, aggression, and anxious/depressed subscales). Subjects were comprehensively assessed at follow-up with structured psychiatric interviews. Data were collected from April 1988 to February 2003.

RESULTS

Over a mean follow-up period of 7.4 years, a positive CBCL-PBD score predicted subsequent diagnoses of bipolar disorder, major depressive disorder, and conduct disorder, as well as impaired psychosocial functioning and higher risk for psychiatric hospitalization.

CONCLUSION

This work suggests that a positive CBCL-PBD score based on elevations on the attention problems, aggressive behavior, and anxious/depressed subscales predicts subsequent pediatric bipolar disorder and associated syndrome-congruent impairments. If confirmed in other studies, the CBCL-PBD score has the potential to help identify children at high risk to develop bipolar disorder.

Investigation of genetically mediated child effects on maltreatment

Theory and empirical evidence suggest that children's genetically influenced characteristics help to shape the environments they experience, including the parenting they 'receive'. The extent of these genetically-mediated child effects on childhood maltreatment is not well known. The present study estimates the magnitude of genetically mediated child effects on maltreatment in 3,297 twins and siblings who were part of a large nationally representative sample of adolescents (ADD health). Participants in early adulthood retrospectively reported their experiences of physical and sexual maltreatment and neglect. Results are consistent with small genetically-mediated child effects on physical maltreatment and neglect, and none on sexual maltreatment, and all three forms of maltreatment are influenced mainly by idiosyncratic individual circumstances.

[To know more about the Prader-Willi syndrome. Multidisciplinary support]

Prader-Willi syndrome, induced by a loss of function of paternal genes in the subcentrometric region of the chromosome 15 (q11.2q13), is a complex neurodevelopmental disorder with characteristic obesity resulting from hyperphagia. In addition behavioural disturbancies with obsessive-compulsive features, aggression, temper tantrums included, are relatively frequently seen and they often require psychiatric intervention. In this part of the paper we reviewed the recent data of behavioural phenotype the correlations of phenotype-genotype and possibilities of the multidisciplinary support for the affected persons and theirs families.

[The Cys allele of the DRD2 (Ser311Cys polymorphism) is associated with schizophrenia and worse sustained attention in patients]

The DRD2 Ser311Cys polymorphism was studied in a sample which included 366 patients with schizophrenia and 387 healthy controls. The frequency of the Cys allele was significantly higher (p<0,009) in the group of patients compared to the controls (8,5% and 3,9%, respectively). Sustained attention assessed by P300 parameters was studied in 66 patients with the SerSer and SerCys genotypes (the CysCys genotype was not observed in the sample studied). A significant effect (p=0,01) of the SerCys genotype on P300 latency in frontal, central and temporal regions was found. Patients with the at-risk allele presented delayed latencies that reflected the lower speed of mental processes related to activation of attention resources. In conclusion, our data support the evidence of association between the Cys allele and schizophrenia obtained earlier for other populations and revealed that carriers of the genotype containing the at-risk allele had delayed P300 latencies.

Are oppositional-defiant and hyperactive-inattentive symptoms developmental precursors to conduct problems in late childhood?: genetic and environmental links

Inattentive-hyperactive and oppositional behavior have been hypothesized to be developmental precursors to conduct problems. We tested these hypotheses using a longitudinal sample of 6,466 offspring of women selected from nationally representative US households. Conduct problems across 8-13 years were robustly predicted by conduct problems at 4-7 years, but also were independently predicted to a small extent by both inattentive-hyperactive and oppositional behaviors at 4-7 years. Longitudinal multivariate behavior genetic analyses revealed that the genetic and environmental factors that influence conduct problems at both 4-7 and 8-13 years also influence the putative precursors at 4-7 years. After genetic and environmental influences on conduct problems at 4-7 years were taken into account, however, inattentive-hyperactive and oppositional behavior at 4-7 years shared causal influences with conduct problems 8-13 years to a negligible extent. These findings suggest that after early conduct problems are controlled, little is gained in terms of prediction or understanding genetic and environmental influences on later child conduct problems by treating early inattentive-hyperactive and oppositional behavior as developmental precursors to later conduct problems.

Parental smoking and adolescent problem behavior: an adoption study of general and specific effects

OBJECTIVE

It is essential to understand the effect of parental smoking on offspring tobacco use. In biologically related families, parents who smoke may transmit a nonspecific genetic risk for offspring disinhibited behavior, including tobacco use. Studying adoptive families allows one to control for genetic confounding when examining the environmental effect of exposure to parental smoking. The purpose of this study was to examine the genetic and environmental contributions to the risk represented by exposure to parental smoking and to assess the specificity of that risk.

METHODS

Adolescents adopted in infancy were systematically ascertained from records of three private Minnesota adoption agencies; nonadopted adolescents were ascertained from Minnesota birth records. Adolescents and their rearing parents participated in all assessments in person. The main outcome measures were self-reports of behavioral deviance, substance use, and personality, as well as DSM-IV clinical assessments of childhood disruptive disorders.

RESULTS

The data from adoptive families suggest that exposure to parental smoking represents an environmental risk for substance use in adolescent offspring. In biologically related families, the effect of exposure to parental smoking is larger and more diverse, including substance use, disruptive behavior disorders, delinquency, deviant peer affiliations, aggressive attitudes, and preference for risk taking.

CONCLUSIONS

This study provides evidence for an environmentally mediated pathway by which parental smoking increases risk specifically for substance use in adolescent offspring. The data are also consistent with a genetically mediated pathway by which nonadoptive parents who smoke may also transmit a nonspecific genetic risk to their offspring for disinhibited behavior.

Rural environments reduce the genetic influence on adolescent substance use and rule-breaking behavior

BACKGROUND

There is increasing evidence that certain environmental factors can modify genetic effects. This is an important area of investigation as such work will help to guide the development of new intervention programs. In this paper, we address whether rural environments moderate the genetic influence on adolescent substance use and rule-breaking behavior (i.e. externalizing psychopathology).

METHOD

Over 1200 Minnesotan 17-year-old twins were classified as either urban or rural. Externalizing behavior was operationalized as the use and abuse of alcohol and drugs along with symptoms of conduct, oppositional defiant, and antisocial personality disorders. Biometric factor modeling estimated whether the relative contribution of genetic and shared environmental factors varied from urban to rural settings.

RESULTS

Residency effects reached statistical significance in the male sample only. In urban environments, externalizing behavior was substantially influenced by genetic factors, but in rural environments, shared environmental factors became more influential. This was apparent at both the individual-variable and factor levels.

CONCLUSIONS

These findings suggest a gene-environment interaction in the development of male adolescents' problem behaviors, including substance use. The results fit within an expanding literature demonstrating both the contextual nature of the heritability statistic and how certain environments may constrain the expression of genetic tendencies.

High heritability for a composite index of children's activity level measures

Despite the high heritability of children's activity level, which forms part of the core symptom domain of hyperactivity-impulsivity within attention deficit hyperactivity disorder (ADHD), there has only been a limited success with identifying candidate genes involved in its etiology. This may reflect a lack of understanding about the different measures used to define activity level across studies. We aimed to study the genetic and environmental etiology across three measures of activity level: parent and teacher ratings of hyperactivity-impulsivity and actigraph measurements, within a population-based sample of 463 7-9 year old twin pairs. We further examined ways in which the three measures could be combined for future molecular studies. Phenotypic correlations across measures were modest, but a common underlying phenotypic factor was highly heritable (92%); as was a simple aggregation of all three measurements (77%). This suggests that distilling what is common to all three measures may be a good method for generating a quantitative trait suitable for molecular studies of activity level in children. The high heritabilities found are encouraging in this respect.

The relationship of maternal smoking to psychological problems in the offspring

There is strong evidence for an association between maternal smoking in pregnancy and psychological problems in offspring. The problems most frequently associated are attention problems, hyperactivity, and conduct problems, although there is some evidence for an association with substance use problems as well. The nature of this association is unclear, but it is likely the result of a number of different mechanisms. Animal studies provide evidence for a causal relationship, in which exposure to nicotine has detrimental effects on foetal development. Other studies suggest that factors that correlate with maternal prenatal smoking may be the real risk factors for behavioural problems, although evidence that the associations remain after controlling for such risks goes some way to dispel this as the only explanation. Finally, maternal prenatal smoking may index underlying psychological problems in the mother that are inherited by the offspring. In all likelihood, a combination of these mechanisms may contribute to observed relationships between prenatal smoking and offspring psychological problems. Now that the association is well established, future research needs to focus more strongly on disentangling underlying mechanisms. Although animal studies demonstrate a casual relationship, it appears from other research that this may not be the whole story in human samples. Furthermore, the relationship may only exist under certain conditions (i.e. against a certain genetic background), and this possibility warrants further examination, particularly in relation to other genetic risks, and outcomes other than ADHD. Application of the children-of-twins design may also cast further light on the processes involved.

Parental diagnoses in youth with narrow phenotype bipolar disorder or severe mood dysregulation

OBJECTIVE

Controversy exists regarding whether nonepisodic irritability and hyperarousal (severe mood dysregulation) is a phenotype of pediatric bipolar disorder. The authors compared axis I diagnoses in parents of children with narrow phenotype bipolar disorder and parents of youth with severe mood dysregulation.

METHOD

Parents of youth with narrow phenotype bipolar disorder (proband N=33, parent N=42) and youth with severe mood dysregulation (proband N=30, parent N=37) were interviewed by clinicians who were blind to the child's diagnostic status using the Diagnostic Interview for Genetic Studies.

RESULTS

Compared to parents of youth with severe mood dysregulation, parents of youth with narrow phenotype bipolar disorder were significantly more likely to be diagnosed with bipolar disorder. There were no other diagnostic differences between the two groups.

CONCLUSIONS

These data suggest that narrow phenotype bipolar disorder may be distinct from severe mood dysregulation in terms of familial aggregation. Additionally, the familiality of narrow phenotype bipolar disorder and adult DSM-IV bipolar disorder is high.

[Association between serotonin 4 gene polymorphisms and attention deficit hyperactivity disorder comorbid or not comorbid disruptive behavioral disorder]

OBJECTIVE

To investigate the relationship between three HTR4 gene polymorphisms, 83097 C>T, 83198 A>G as well as -36C>T polymorphisms, and attention deficit hyperactivity disorder (ADHD) comorbid or not comorbid disruptive behavioral disorder (DBD).

METHODS

Blood samples were taken from 152 trios with probands of ADHD comorbid DBD and 173 trios with probands of ADHD not comorbid DBD. DNA was extracted. 83097 C>T, 83198 A>G and -36C>T were genotyped by restriction fragment length polymorphism analysis. Transmit/disequilibrium test and haplotype analysis were used to test the association of the three polymorphisms with ADHD comorbid or not comorbid DBD separately.

RESULTS

Haplotype T/G/T showed tendency of over transmission (chi(2)=3.470,P=0.062) to probands of ADHD with DBD, while haplotype C/G/T (chi(2)=4.568,P=0.032) and C/G/C (chi(2)=5.333,P=0.021) were under transmitted to probands of ADHD without DBD, No biased transmissions of any allele were found in families with probands of ADHD with and without DBD.

CONCLUSION

Whether ADHD comorbid DBD or not comorbid DBD makes difference at the level of HTR4 gene polymorphisms.

[Association analysis of dopamine D4 receptor gene polymorphism and attention deficit hyperactivity disorder with/without disruptive behavior disorder]

OBJECTIVE

To examine the role of dopamine D4 receptor gene (DRD4) in attention deficit hyperactivity disorder (ADHD) with/without disruptive behavior disorder (DBD) by focusing on a-521C/T SNP within the promoter region of this gene.

METHODS

A total of 401 DSM-IV ADHD children (including 284 trios) of Chinese Han descent were genotyped. Chi-square test and the transmission disequilibrium test (TDT) were used to test for associations in ADHD with and without DBD respectively.

RESULTS

In the comparison of ADHD with (n=143) and without (n=258) DBD, the -521T allele ( chi(2) = 6.778, P= 0.009, OR= 1.485) and the TT genotype (chi(2) = 6.292,P=0.012,OR=1.729) showed higher frequency in children with ADHD and DBD simultaneously. For family based analysis, T allele of the -521C/T polymorphism was preferentially transmitted to ADHD children with comorbid DBD (n=100, chi(2) = 3.868,P=0.049), whereas no significant distortion was found in the transmission of the tested variant for ADHD without DBD (n=184, chi(2) = 0.223, P=0.637).

CONCLUSION

Our findings suggest that the -521C/T SNP of DRD4 may contribute to the predisposition to ADHD with comorbid DBD. This study supports for the hypothesis that ADHD with comorbid DBD may be influenced by greater genetic effect compared to ADHD alone.

Attention-deficit/hyperactivity disorder and comorbid disruptive behavior disorders: evidence of pleiotropy and new susceptibility loci

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) comorbid with oppositional defiant disorder (ODD) or conduct disorder (CD) and substance abuse/dependence seems to represent a specific subset within the phenotypic ADHD spectrum.

METHODS

We applied complex segregation and linkage analyses in a set of multigenerational families densely segregating ADHD comorbid with ODD, CD, alcohol abuse/dependence, and nicotine dependence.

RESULTS

Our data suggest that ADHD cosegregates with disruptive behaviors as a unique, phenotypically variable trait as evidenced by highly significant pair-wise linkages among: ADHD and ODD (logarithm of odds [LOD]=14.19), ADHD and CD (LOD=5.34), ODD and CD (LOD=6.68), and CD and alcohol abuse/dependence (LOD=3.98). In addition to previously reported ADHD susceptibility loci, we found evidence of linkage for comorbid ADHD phenotypes to loci at 8q24, 2p21-22.3, 5p13.1-p13.3, 12p11.23-13.3, 8q15, and 14q21.1-22.2. These results were replicated with an affected status phenotype derived from latent class clusters.

CONCLUSIONS

Patterns of cosegregation of ADHD with comorbidities can inform our understanding of the inheritance patterns not only of ADHD but also of disruptive behavioral disorders and alcohol abuse/dependence. Refining the comorbid ADHD phenotype by determining the cosegregation profile of specific comorbidities might be a powerful tool for defining significant regions of linkage.

[Association between serotonin 2C gene polymorphisms and attention deficit hyperactivity disorder in children with or without comorbidity of disruptive behavior disorder]

OBJECTIVE

Disruptive behavior disorder (DBD) is one of the main comorbidity of attention deficit hyperactivity disorder (ADHD). Previous studies showed significantly different serotonin function between ADHD children with and without the comorbidity of DBD. Therefore, it is needed to compare these two groups in terms of serotonin receptor gene polymorphisms, which may provide further evidence for the previous studies. The current study aimed to investigate the relationship between two serotonin receptor 2C (HTR2C) gene polymorphisms, that are C-759T and G-697C polymorphisms, and ADHD with or without concomitant DBD.

METHOD

Blood samples were taken from 237 trios with probands of ADHD with DBD comorbidity and 251 trios with probands of ADHD without comorbidity of DBD. All the subjects were from the ADHD clinic of Peking University Sixth Hospital. DNA was extracted and PCR was performed to amplify the fragments containing both C-759T and G-697C polymorphisms. AciI was used to detect different alleles of the two polymorphisms. Both allele-based and haplotype-based TDT analyses were used to test the association of the two polymorphisms of HTR2C gene and ADHD with or without comorbidity of DBD.

RESULTS

The haplotypes -759C (chi(2) = 4.25, P = 0.04), -697G(chi(2) = 3.21, P = 0.07), as well as -759C/-697G were over-transmitted (chi(2) = 4.31, P = 0.04) to the probands of ADHD without DBD. No biased transmission of any allele and haplotype were found in families with probands of ADHD with DBD.

CONCLUSION

ADHD with or without the comorbidity DBD was different at the level of HTR2C gene polymorphisms of C-759T and G-697C. HTR2C is related to ADHD without DBD, while not related to ADHD with DBD. The results suggested that the two groups may have different genetic background, at least in HTR2C.

Assessment and etiology of attention deficit hyperactivity disorder and oppositional defiant disorder in boys and girls

Attention deficit hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) are more common in boys than girls. In this paper, we investigated whether the prevalence differences are attributable to measurement bias. In addition, we examined sex differences in the genetic and environmental influences on variation in these behaviors. Teachers completed the Conners Teacher Rating Scale-Revised:Short version (CTRS-R:S) in a sample of 800 male and 851 female 7-year-old Dutch twins. No sex differences in the factor structure of the CTRS-R:S were found, implying the absence of measurement bias. The heritabilities for both ADHD and ODD were high and were the same in boys and girls. However, partly different genes are expressed in boys and girls.

Association of dopamine transporter genotype with disruptive behavior disorders in an eight-year longitudinal study of children and adolescents

Associations between dopamine transporter (DAT1) variable number tandem repeats (VNTR), genotypes, and disruptive behavior were examined in an 8-year longitudinal study of children (n = 183). Half of the children met criteria for attention-deficit/hyperactivity disorder (ADHD) at 4-6 years and half were non-referred comparison children. Consistent with several studies, the non-additive association for the 10-repeat allele was significant for hyperactivity-impulsivity (HI) symptoms. However, consistent with other studies, exploratory analyses of the non-additive association of the 9-repeat allele of DAT1 with HI and oppositional defiant disorder (ODD) symptoms also were significant. The inconsistent association between DAT1 and child behavior problems in this and other samples may reflect joint influence of the 10-repeat and 9-repeat alleles.

Patterns of psychopathology in the families of children with conduct problems, depression, and both psychiatric conditions

Comorbid conduct problems (CPs) and depression are observed far more often than expected by chance, which is perplexing given minimal symptom overlap. In this study, relations between parental psychopathology and children's diagnostic status were evaluated to test competing theories of comorbidity. Participants included 180 families with an 8-12-year-old child diagnosed with CPs, depression, both conditions, or neither condition. Although no single theory of comorbidity was supported fully, evidence suggested that CPs and depression may be inherited separately. Paternal antisocial characteristics and maternal depression provided independent prediction of both child depression and CPs. However, paternal antisocial behavior moderated the effect of maternal depression on CPs. For children with antisocial fathers, CPs were observed regardless of maternal depression levels. In contrast, a strong relation was observed between CPs and maternal depression for children without antisocial fathers.

Gray matter volume abnormalities and externalizing symptoms in subjects at high risk for alcohol dependence

Reduced right amygdala volumes have been reported in young, alcohol-naïve subjects at high risk (HR) for alcohol dependence. The differences in brain morphometry have been associated with an excess of externalizing behaviors in these subjects. This may reflect a neurobiological vulnerability to alcohol dependence. Existing Magnetic Resonance Imaging (MRI) studies on these subjects have examined only a few, pre-selected brain regions using the manual regions of interest (ROI) approach. MRI of HR subjects (n = 20) and age, sex, and handedness-matched low-risk (LR) subjects (n = 21) were analyzed using optimized voxel-based morphometry and ROI approach. The externalizing symptoms of these subjects and their fathers were measured using the Semi-Structured Assessment for the Genetics of Alcoholism. HR subjects had significantly smaller volumes of superior frontal, cingulate and parahippocampal gyri, amygdala, thalamus and cerebellum. These gray matter volumes correlated negatively with externalizing symptoms scores. Subjects at HR for alcoholism have reduced volumes of critical areas of brain gray matter, which are associated with increased externalizing symptoms. These represent key endophenotypes of alcoholism.

Parent-of-origin effects in attention-deficit hyperactivity disorder

The goal of the present study was to investigate parent-of-origin effects in attention-deficit hyperactivity disorder (ADHD). Parent-of-origin effects in ADHD may be due to differences in the relative quantity of risk factors transmitted by each parent. Alternatively, parent-of-origin effects may be produced by qualitative differences in the risks transmitted, such as those carried on the sex chromosomes or regulated by genomic imprinting. 60 children with maternal-only history of ADHD and 131 children with paternal-only history of ADHD were compared on three domains for which prior evidence suggested parent-of-origin effects may exist: core symptoms, disruptive behaviours and depression. Dependent variables were derived from previously validated, age-appropriate and standardized parent and teacher interviews and questionnaires. Depression levels were rated using the Child Depression Inventory. Consistent with previous research and the predictions derived from threshold models of ADHD etiology, the maternal history group received higher ratings of behavioural disorder (ADHD, conduct disorder and oppositional symptoms) than the paternal history group. Parent-of-origin effects were also observed for depression, with the paternal history group rating themselves as significantly more depressed than children in the maternal history group, particularly girls. Heightened paternal transmission relative to maternal is suggestive of genomic imprinting, and the interaction with proband sex indicates the involvement of the sex chromosomes or sex-specific physiological or hormonal factors. Interpretations of these data in terms of environmental and genetic factors, including epigenetic and sex-linked hypotheses, are explored.

Autistic-spectrum disorders in Down syndrome: further delineation and distinction from other behavioral abnormalities

The present study extends our previous work characterizing the behavioral features of autistic-spectrum disorder (ASD) in Down syndrome (DS) using the Aberrant Behavior Checklist (ABC) and Autism Behavior Checklist (AutBehav). We examined which specific behaviors distinguished the behavioral phenotype of DS + ASD from other aberrant behavior disorders in DS, by determining the relative contribution of ABC and AutBehav subscales and items to the diagnosis of ASD. A total of 127 subjects (aged 2-24 years; mean age: 8.4 years; approximately 70% male), comprising: a cohort of 64 children and adolescents with DS and co-morbid ASD (DS + ASD), 19 with DS and stereotypic movement disorder (DS + SMD), 18 with DS and disruptive behaviors (DS + DB), and 26 with DS and no co-morbid behavior disorders (DS + none) were examined using the aforementioned measures of aberrant behavior. We found that subjects with DS + ASD showed the most severe aberrant behavior, especially stereotypy compared to DS + none and lethargy/social withdrawal and relating problems compared to DS + SMD. Specifically, relatively simple stereotypic behavior differentiated DS + ASD from DS + DB, whereas odd/bizarre stereotypic and anxious behavior characterized DS + ASD relative to DS + SMD and DS + none. Additionally, in a subset of subjects with DS + ASD and anxiety, social withdrawal was particularly pronounced. Overall, our findings indicate that a diagnosis of DS + ASD represents a distinctive set of aberrant behaviors marked by characteristic odd/bizarre stereotypic behavior, anxiety, and social withdrawal.

Genetische Befunde bei der Aufmerksamkeitsdefizit- und Hyperaktivitätsstörung (ADHS)

Zusammenfassung: Die Aufmerksamkeitsdefizit- und Hyperaktivitätsstörung (ADHS) ist mit einer Prävalenz von 3-7% eine häufige kinder- und jugendpsychiatrische Störung. Auf der Basis formalgenetischer Studien ergibt sich eine Heritabilitätsschätzung von 60-80% für ADHS mit einem ca. 5-fach erhöhten Risiko für erstgradige Verwandte von Betroffenen. Bislang vier Genomscans lieferten potentiell relevante chromosomale Regionen, insbesondere den einheitlichen Kopplungsbefund auf 5p13. Aus einer Vielzahl von Assoziationsstudien zu Kandidatengenen deuten aktuelle Metaanalysen auf die Relevanz der Gene der dopaminergen Rezeptoren DRD4 und DRD5 sowie des serotonergen Rezeptors HTR1B und des Synaptosomal Assoziierten Proteins (SNAP-25). In Tiermodellen liegen vorwiegend Paradigmen für Hyperaktivität vor; diese sind in knockout- und Quantitative Trait Loci (QTL) Designs mit viel versprechenden Ergebnissen zum dopaminergen System untersucht worden. Es ist davon auszugehen, dass erst das Zusammenwirken verschiedener Gen-Varianten mit jeweils moderatem bis hin zu kleinem Effekt den Phänotyp ADHS bedingen (Oligo-/ Polygenie) und bei verschiedenen Betroffenen unterschiedliche Kombinationen von prädisponierenden Gen-Polymorphismen zu ADHS führen können. Entsprechend sind für molekulargenetische Studien große Fallzahlen notwendig und die bisherigen Befunde als vorläufig zu interpretieren. Zukunftsweisend für die molekulargenetische Aufklärung von ADHS sind SNP-basierte Genomscans, mit denen 10 000-1 000 000 einzelne Polymorphismen (SNPs) gleichzeitig untersucht werden können. Tiermodelle liefern Hinweise auf die Funktion relevanter Kandidatengene und tragen zur Erweiterung der bislang teilweise widersprüchlichen Kenntnisse zur Neurobiologie des ADHS bei.

[Association between serotonin 1D gene polymorphisms and attention deficit hyperactivity disorder comorbid or not comorbid disruptive behavior disorder]

OBJECTIVE

To investigate the relationship between two HTR1D gene polymorphisms, that is 1350T > C and 1236A > G polymorphisms, and attention deficit hyperactivity disorder (ADHD) comorbid or not comorbid disruptive behavior disorder (DBD).

METHODS

Blood samples were taken from 90 trios with probands of ADHD comrbid DBD and 182 trios with probands of ADHD not comorbid DBD. DNA was extracted. 1350T > C and 1236A > G were genotyped by restriction fragment length polymorphism analysis. Transmit/disequilibrium test and haplotype analysis were used to test the association of the two polymorphisms of HTR1D gene and ADHD comorbid or not comorbid disruptive behavior disorder (DBD) separately.

RESULTS

1350T allele(chi2 = 3.67, P = 0.055)and G/T haplotype(chi2 = 3.84, P = 0.050)were overtransmitted, while 1350C allele(chi2 = 3.67, P = 0.055) and G/C haplotype(chi2 = 5.22, P = 0.022)were undertransmitted to probands of ADHD with DBD. No biased transmission of any allele and haplotype was found in families with probands of ADHD without DBD.

CONCLUSION

ADHD comorbid or not comorbid DBD are different at the level of HTR1D gene polymrohisms of 1350T > C and 1236A > G. The current results indicate that ADHD with DBD has more heritable backgrounds when compared with ADHD without DBD.

Adult outcomes of attention deficit hyperactivity disorder and conduct disorder: are the risks independent or additive?

METHODS

Data were obtained from a longitudinal study sample of 754 adoptees and categorized based on review of the available adoption agency, medical, and psychiatric records of the biological parents. Categorical data were analyzed using chi2 or Fisher's exact tests, as appropriate. Logistic regression analyses were used to assess the relative contribution of variables.

RESULTS

There was not a statistically significant difference in the frequency or type of self-reported adult disruptive behavior, arrests, jail stays, felony arrests, or frequency of conduct disorder (CD) when inattentiveness, impulsivity, and hyperactivity were analyzed individually. The contributions of attention deficit hyperactivity disorder (ADHD) were independent and no additional increased risk for future illegal behavior was conferred by the combination of the disorders. While the effect of CD on illegal behavior was correlated with substance abuse and dependence, ADHD continued to be a significant contributor after controlling for substance abuse and dependence.

CONCLUSIONS

Data indicated that ADHD and CD are related but different disorders conferring risk for adult illegal behavior or arrest. In this sample, inattention was the most common domain impaired among those with ADHD, followed closely by hyperactivity, with impulsivity reported least often among those endorsing symptoms of ADHD.

MAOA, maltreatment, and gene-environment interaction predicting children's mental health: new evidence and a meta-analysis

Previous research on adults has shown that a functional polymorphism in the promoter region of the monoamine oxidase A (MAOA) gene moderates the impact of childhood maltreatment on risk for developing antisocial behavior. Thus far, attempts to replicate this finding have been mixed. The current study (i) presents new data investigating this finding in a sample of 975 seven-year-old boys, and (ii) evaluates the extant data by conducting a meta-analysis of published findings. We replicated the original finding by showing that the MAOA polymorphism moderates the development of psychopathology after exposure to physical abuse, we extended the finding to childhood closer in time to the maltreatment experience, and we ruled-out the possibility of a spurious finding by accounting for passive and evocative gene-environment correlation. Moreover, meta-analysis demonstrated that across studies, the association between maltreatment and mental health problems is significantly stronger in the group of males with the genotype conferring low vs high MAOA activity. These findings provide the strongest evidence to date suggesting that the MAOA gene influences vulnerability to environmental stress, and that this biological process can be initiated early in life.