Label-free, live optical imaging of reprogrammed bipolar disorder patient-derived cells reveals a functional correlate of lithium responsiveness

Development of novel treatments and diagnostic tools for psychiatric illness has been hindered by the absence of cellular models of disease. With the advent of cellular reprogramming, it may be possible to recapitulate the disease biology of psychiatric disorders using patient skin cells transdifferentiated to neurons. However, efficiently identifying and characterizing relevant neuronal phenotypes in the absence of well-defined pathophysiology remains a challenge. In this study, we collected fibroblast samples from patients with bipolar 1 disorder, characterized by their lithium response (n=12), and healthy control subjects (n=6). We identified a cellular phenotype in reprogrammed neurons using a label-free imaging assay based on a nanostructured photonic crystal biosensor and found that an optical measure of cell adhesion was associated with clinical response to lithium treatment. This cellular phenotype may represent a useful biomarker to evaluate drug response and screen for novel therapeutics.

Influence of the COMT val(108/158)met polymorphism on continuous performance task indices

The Continuous Performance Task (CPT) is a widely-used measure of sustained attention and impulsivity. Deficits in CPT performance have been found in several psychiatric disorders, such as Attention-Deficit/Hyperactivity Disorder (ADHD) and schizophrenia. Molecular genetic studies of CPT performance are currently limited and have generally revealed inconsistent findings. The current study tested the associations of the COMT val(108/158)met polymorphism with AX-CPT indices (i.e., omission and commission errors, d׳, and lnβ), as well as the variability of these indices across blocks, in a sample of clinic-referred and non-referred children (N=380). We found significant associations between COMT and variability in the Signal Detection Theory (SDT) indices d׳ and lnβ across blocks, as well as a statistical trend for association between COMT and commission errors. Higher externalizing psychopathology was associated with general impairment on AX-CPT performance, and for some indices (i.e., d׳ variability and lnβ variability) the effect of COMT was stronger at higher levels of psychopathology. Our findings support the role of COMT in components of CPT performance and highlight the potential utility of using SDT indices, particularly in relation to variability in performance. Moreover, our results suggest that for some indices the effect of COMT is stronger at higher levels of externalizing psychopathology. Our study yields some preliminary insights regarding the neurobiology of CPT performance, which may elucidate the mechanisms by which specific genes confer risk for various cognitive deficits, as well as relevant disorders characterized by these deficits.

Candidate genes for aggression and antisocial behavior: a meta-analysis of association studies of the 5HTTLPR and MAOA-uVNTR

Variation in central serotonin levels due to genetic mutations or experimental modifications has been associated with the manifestation of aggression in humans and animals. Many studies have examined whether common variants in serotonergic genes are implicated in aggressive or antisocial behaviors (ASB) in human samples. The two most commonly studied polymorphisms have been the serotonin transporter linked polymorphic region of the serotonin transporter gene (5HTTLPR) and the 30 base pair variable number of tandem repeats of the monoamine oxidase A gene (MAOA-uVNTR). Despite the aforementioned theoretical justification for these polymorphisms, findings across studies have been mixed and are thus difficult to interpret. A meta-analysis of associations of the 5HTTLPR and MAOA-uVNTR with ASB was conducted to determine: (1) the overall magnitude of effects for each polymorphism, (2) the extent of heterogeneity in effect sizes across studies and the likelihood of publication bias, and (3) whether sample-level or study-level characteristics could explain observed heterogeneity across studies. Both the 5HTTLPR and the MAOA-uVNTR were significantly associated with ASB across studies. There was also significant and substantial heterogeneity in the effect sizes for both markers, but this heterogeneity was not explained by any sample-level or study-level characteristics examined. We did not find any evidence for publication bias across studies for the MAOA-uVNTR, but there was evidence for an oversampling of statistically significant effect sizes for the 5HTTLPR. These findings provide support for the modest role of common serotonergic variants in ASB. Implications regarding the role of serotonin in antisocial behavior and the conceptualization of antisocial and aggressive phenotypes are discussed.

Genetic imaging of the association of oxytocin receptor gene (OXTR) polymorphisms with positive maternal parenting

Background: Well-validated models of maternal behavior in small-brain mammals posit a central role of oxytocin in parenting, by reducing stress and enhancing the reward value of social interactions with offspring. In contrast, human studies are only beginning to gain insights into how oxytocin modulates maternal behavior and affiliation.

Methods: To explore associations between oxytocin receptor genes and maternal parenting behavior in humans, we conducted a genetic imaging study of women selected to exhibit a wide range of observed parenting when their children were 4–6 years old.

Results: In response to child stimuli during functional magnetic resonance imaging (fMRI), hemodynamic responses in brain regions that mediate affect, reward, and social behavior were significantly correlated with observed positive parenting. Furthermore, single nucleotide polymorphisms (SNPs) (rs53576 and rs1042778) in the gene encoding the oxytocin receptor were significantly associated with both positive parenting and hemodynamic responses to child stimuli in orbitofrontal cortex (OFC), anterior cingulate cortex (ACC), and hippocampus.

Conclusions: These findings contribute to the emerging literature on the role of oxytocin in human social behavior and support the feasibility of tracing biological pathways from genes to neural regions to positive maternal parenting behaviors in humans using genetic imaging methods.

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.

The Double-Edged Sword of Grandiose Narcissism

Recent research and theorizing suggest that narcissism may predict both positive and negative leadership behaviors. We tested this hypothesis with data on the 42 U.S. presidents up to and including George W. Bush, using (a) expert-derived narcissism estimates, (b) independent historical surveys of presidential performance, and (c) largely or entirely objective indicators of presidential performance. Grandiose, but not vulnerable, narcissism was associated with superior overall greatness in an aggregate poll; it was also positively associated with public persuasiveness, crisis management, agenda setting, and allied behaviors, and with several objective indicators of performance, such as winning the popular vote and initiating legislation. Nevertheless, grandiose narcissism was also associated with several negative outcomes, including congressional impeachment resolutions and unethical behaviors. We found that presidents exhibit elevated levels of grandiose narcissism compared with the general population, and that presidents’ grandiose narcissism has been rising over time. Our findings suggest that grandiose narcissism may be a double-edged sword in the leadership domain.

A sibling-comparison study of smoking during pregnancy and childhood psychological traits

Prenatal exposure to substances of abuse is associated with numerous psychological problems in offspring, but quasi-experimental studies controlling for co-occurring risk factors suggest that familial factors (e.g., genetic and environmental effects shared among siblings) confound many associations with maternal smoking during pregnancy (SDP). Few of the quasi-experimental studies in this area have explored normative psychological traits in early childhood or developmental changes across the lifespan, however. The current study used multilevel growth curve models with a large, nationally-representative sample in the United States to investigate for potential effects of SDP on the developmental trajectories of cognitive functioning, temperament/personality, and disruptive behavior across childhood, while accounting for shared familial confounds by comparing differentially exposed siblings and statistically controlling for offspring-specific covariates. Maternal SDP predicted the intercept (but not change over time) for all cognitive and externalizing outcomes. Accounting for familial confounds, however, attenuated the association between SDP exposure and all outcomes, except the intercept (age 5) for reading recognition. These findings, which are commensurate with previous quasi-experimental research on more severe indices of adolescent and adult problems, suggest that the associations between SDP and developmental traits in childhood are due primarily to confounding factors and not a causal association.

Does low birth weight share common genetic or environmental risk with childhood disruptive disorders?

Although advances in neonatal care over the past century have resulted in increased rates of survival among at-risk births, including infants with low birth weight, we have much to learn about psychological outcomes in this population. In particular, despite growing evidence that low birth weight may be associated with an increased risk for Attention-Deficit/Hyperactive Disorder (ADHD) symptoms in childhood, few studies have examined birth weight as a risk factor for disruptive disorders that commonly co-occur with ADHD. In addition, the etiology of the relation between birth weight and these disorders is unknown. The current investigation aimed to better understand these associations in the context of potentially confounding genetic and environmental influences by examining phenotypic associations between birth weight and disruptive disorder symptoms both between families and within families in two independent twin samples (Sample 1: N = 1,676 individuals; Sample 2: N = 4,038 individuals). We found negative associations between birth weight and inattentive, hyperactive-impulsive, and broad externalizing symptoms in both samples. Nonetheless, the overall magnitude of these associations was very small, contributing to less than 1% of the variance in these symptom dimensions. Within-family associations between birth weight and disruptive disorder symptoms did not differ for monozygotic and dizygotic twin pairs, suggesting that nonshared environmental influences rather than common genetic influences are responsible for these associations. Overall, the consistent albeit weak associations between birth weight and disruptive disorder symptoms suggest that low birth weight may not represent a major risk factor in the development of these symptoms.

Early concern and disregard for others as predictors of antisocial behavior

BACKGROUND

Prediction of antisocial behavior is important, given its adverse impact on both the individuals engaging in antisocial behavior and society. Additional research identifying early predictors of future antisocial behavior, or antisocial propensity, is needed. The present study tested the hypothesis that both concern for others and active disregard for others in distress in toddlers and young children predict antisocial behavior during middle childhood and adolescence.

METHODS

A representative sample of same-sex twins (N=956) recruited in Colorado was examined. Mother-rated and researcher-observed concern and disregard for others assessed at age 14-36 months were examined as predictors of parent- (age 4-12), teacher- (age 7-12), and self-reported (age 17) antisocial behavior.

RESULTS

  Observed disregard for others predicted antisocial behavior assessed by three different informants (parents, teachers, and self), including antisocial behavior assessed 14 years later. It also predicted a higher order antisocial behavior factor (β=.58, p<.01) after controlling for observed concern for others. Mother-rated disregard for others predicted parent-reported antisocial behavior. Contrary to predictions, neither mother-rated nor observed concern for others inversely predicted antisocial behavior. RESULTS of twin analyses suggested that the covariation between observed disregard for others and antisocial behavior was due to shared environmental influences.

CONCLUSIONS

Disregard for others in toddlerhood/early childhood is a strong predictor of antisocial behavior in middle childhood and adolescence. The results suggest the potential need for early assessment of disregard for others and the development of potential interventions.

The role of language in concern and disregard for others in the first years of life

We examined the associations between language skills and concern and disregard for others in young children assessed longitudinally at ages 14, 20, 24, and 36 months, testing the hypothesis that language skills have a specific role (distinct from that of general cognitive ability) in the development of concern and disregard for others. We found that higher language skills predicted higher concern for others and lower disregard for others even after controlling for general cognitive ability, whereas the association between general cognitive ability and concern/disregard for others was not significant after controlling for language skills. Language skills at 14 months predicted concern for others at 36 months, and results suggested that the relations between language skills and concern and disregard for others begin early in development. Gender differences in concern and disregard for others were at least partially explained by differences in language skills. These results support the specific role of language skills in concern and disregard for others.

Preliminary genetic imaging study of the association between estrogen receptor-α gene polymorphisms and harsh human maternal parenting

A failure of neural changes initiated by the estrogen surge in late pregnancy to reverse the valence of infant stimuli from aversive to rewarding is associated with dysfunctional maternal behavior in nonhuman mammals. Estrogen receptor-α plays the crucial role in mediating these neural effects of estrogen priming. This preliminary study examines associations between estrogen receptor-α gene polymorphisms and human maternal behavior. Two polymorphisms were associated with human negative maternal parenting. Furthermore, hemodynamic responses in functional magnetic resonance imaging to child stimuli in neural regions associated with social cognition fully mediated the association between genetic variation and negative parenting. This suggests testable hypotheses regarding a biological pathway between genetic variants and dysfunctional human maternal parenting.

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.

Dose effects and comparative effectiveness of extended release dexmethylphenidate and mixed amphetamine salts

OBJECTIVE

To compare the dose effects of long-acting extended-release dexmethylphenidate (ER d-MPH) and ER mixed amphetamine salts (ER MAS) on attention-deficit/hyperactivity disorder (ADHD) symptom dimensions, global and specific impairments, and common adverse events associated with stimulants.

METHODS

Fifty-six children and adolescents with ADHD participated in an 8-week, double-blind, crossover study comparing ER d-MPH (10, 20, 25-30 mg) and ER MAS (10, 20, 25-30) with a week of randomized placebo within each drug period. Efficacy was assessed with the ADHD Rating Scale-IV (ADHD-RS-IV), whereas global and specific domains of impairment were assessed with the Clinical Global Impressions Severity and Improvement Scales and the parent-completed Weiss Functional Impairment Scale, respectively. Insomnia and decreased appetite, common stimulant-related adverse events, were measured with the parent-completed Stimulant Side Effects Rating Scale.

RESULTS

Both ER d-MPH and ER MAS were associated with significant reductions in ADHD symptoms. Improvement in Total ADHD and Hyperactivity/Impulsivity symptoms were strongly associated with increasing dose, whereas improvements in Inattentive symptoms were only moderately associated with dose. About 80% demonstrated reliable change on ADHD-RS-IV at the highest dose level of ER MAS compared with 79% when receiving ER d-MPH. Decreased appetite and insomnia were more common at higher dose levels for both stimulants. Approximately 43% of the responders were preferential responders to only one of the stimulant formulations.

CONCLUSIONS

Dose level, rather than stimulant class, was strongly related to medication response.

Alcohol and aggressive behavior in men--moderating effects of oxytocin receptor gene (OXTR) polymorphisms

We explored if the disposition to react with aggression while alcohol intoxicated was moderated by polymorphic variants of the oxytocin receptor gene (OXTR). Twelve OXTR polymorphisms were genotyped in 116 Finnish men [aged 18-30, M = 22.7, standard deviation (SD) = 2.4] who were randomly assigned to an alcohol condition in which they received an alcohol dose of 0.7 g pure ethanol/kg body weight or a placebo condition. Aggressive behavior was measured using a laboratory paradigm in which it was operationalized as the level of aversive noise administered to a fictive opponent. No main effects of the polymorphisms on aggressive behavior were found after controlling for multiple testing. The interactive effects between alcohol and two of the OXTR polymorphisms (rs4564970 and rs1488467) on aggressive behavior were nominally significant and remained significant for the rs4564970 when controlled for multiple tests. To the best of our knowledge, this is the first experimental study suggesting interactive effects of specific genetic variants and alcohol on aggressive behavior in humans.

A quasi-experimental analysis of the influence of neighborhood disadvantage on child and adolescent conduct problems

A quasi-experimental comparison of cousins differentially exposed to levels of neighborhood disadvantage (ND) was used with extensive measured covariates to test the hypothesis that neighborhood risk has independent effects on youth conduct problems (CPs). Multilevel analyses were based on mother-rated ND and both mother-reported CPs across 4-13 years (n = 7,077) and youth-reported CPs across 10-13 years (n = 4,524) from the Children of the National Longitudinal Survey of Youth. ND was robustly related to CPs reported by both informants when controlling for both measured risk factors that are correlated with ND and unmeasured confounds. These findings are consistent with the hypothesis that ND has influence on conduct problems.

Shared genetic influences on negative emotionality and major depression/conduct disorder comorbidity

OBJECTIVE

To investigate whether genetic contributions to major depressive disorder and conduct disorder comorbidity are shared with genetic influences on negative emotionality.

METHOD

Primary caregivers of 2,022 same- and opposite-sex twin pairs 6 to 18 years of age comprised a population-based sample. Participants were randomly selected across five regions in Tennessee, with stratification by age and geographic location. Face-to-face structured interviews were conducted with the primary caregiver of a representative sample of twins.

RESULTS

After accounting for genetic influences on negative emotionality, genetic influences on major depressive disorder/conduct disorder comorbidity were nonsignficant, but only in male twins. Specifically, 19% of the variance in the two disorders was accounted for by genetic factors shared with negative emotionality in male twins. Although the full hypothesis could not be tested in female twins, 10% to 11% of the variance in the two disorders was also accounted for by genetic factors shared with negative emotionality. Common shared environmental and nonshared environmental influences were found for major depressive disorder/conduct disorder comorbidity in male and female twins.

CONCLUSIONS

Negative emotionality represents an important dispositional trait that may explain genetic influences on major depressive disorder/conduct disorder comorbidity, at least for boys. Models of major depressive disorder/conduct disorder comorbidity must simultaneously measure common and specific genetic and environmental factors for a full understanding of this phenomenon. Gender differences require specific research attention in dispositional factors and developmental progression.

Interactions between early parenting and a polymorphism of the child's dopamine transporter gene in predicting future child conduct disorder symptoms

Mounting evidence suggests that genetic risks for mental disorders often interact with the social environment, but most studies still ignore environmental moderation of genetic influences. The authors tested interactions between maternal parenting and the variable number tandem repeat (VNTR) polymorphism in the 3' untranslated region of the dopamine transporter gene in the child to increase understanding of gene-environment interactions involving early parenting. Participants were part of a 9-year longitudinal study of 4- to 6-year-old children who met criteria for attention-deficit/hyperactivity disorder (ADHD) and demographically matched controls. Maternal parenting was observed during standard mother-child interactions in Wave 1. The child's conduct disorder (CD) symptoms 5-8 years later were measured using separate structured diagnostic interviews of the mother and youth. Controlling for ADHD symptoms and child disruptive behavior during the mother-child interaction, there was a significant inverse relation between levels of both positive and negative parenting at 4-6 years and the number of later CD symptoms, but primarily among children with 2 copies of the 9-repeat allele of the VNTR. The significant interaction with negative parenting was replicated in parent and youth reports of CD symptoms separately.

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.

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.

Etiology and measurement of relational aggression: A multi-informant behavior genetic investigation

Although the study of relational aggression is gaining attention in the literature, little is known about the underlying causes of this behavior and the relative validity of various informants. These issues were addressed in a sample of 1,981 6- to 18-year-old twin pairs (36% female, 34% male, 30% opposite-sex). Relational aggression was assessed via maternal and self-report using a structured interview. Univariate models estimated genetic and environmental influences by informant and examined evidence for gender differences. A psychometric model combined data from both informants to estimate etiologic influences that were both common to the informants and informant specific. In both sexes, the latent variable reflecting the mother's and child's shared perception of the child's relational aggression was substantially influenced by both additive genetic (63%) and shared environmental (37%) influences, although this latent variable accounted for much greater variance in the maternal report (66%) than it did in the youth report (9%). In addition, informant-specific additive genetic and shared environmental influences were found only for the youth report, with all remaining variance in the mother's report attributed to nonshared environmental influences. Results are discussed in the context of measuring relational aggression and the importance of multiple informants.

Psychometrics of a self-report version of the Child and Adolescent Dispositions Scale

Lahey and Waldman (2003, 2005) proposed a model in which three dispositions-sympathetic response to others; negative emotional response to threat, frustration, and loss; and positive response to novelty and risk-transact with the environment to influence risk for conduct disorder (CD). To test this model, the Child and Adolescent Dispositions Scale (CADS) was developed to measure these dispositions using parent ratings of the child. Here we report psychometric evaluations of a parallel youth self-report version (CADS-Y). Exploratory factor analysis of CADS-Y items among 832 9- to 17-year-olds yielded a 3-factor structure that was consistent with the model and invariant across sex and informants. In 1,582 pairs of 9- to 17-year-old twins, confirmatory factor analyses supported the CADS-Y 3-factor model. Each CADS-Y dimension was associated with CD and related personality dimensions as predicted.

Developmental structure of genetic influences on antisocial behavior across childhood and adolescence

It is necessary to determine if causal influences on developing antisocial behavior change with age to guide both research and theory on its origins. The extent to which the same genetic factors influence antisocial behavior across 4-17 years of age was estimated using 2,482 sibling pairs of varying genetic relatedness. Assessments of antisocial behavior by mothers (4-9 years), mothers and youth (10-13 years), and youth (14-17 years) reflected the changing validity of informants across development. Genetic influences on antisocial behavior at 14-17 years were entirely shared with those on antisocial behavior at 10-13 years according to both informants. Genetic influences on antisocial behavior at 14-17 years were distinct from those at 4-9 years, however. These age differences in genetic influences cannot be fully distinguished from informant differences across age, but the present findings indicate that youth reported to be persistently antisocial during childhood and adolescence are influenced by one set of genetic factors influencing parent-report conduct problems in childhood and a second set of genetic influences on youth-reported delinquency that come into play around the time of the pubertal transition.

Gene-environment interactions in attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a heterogeneous disorder characterized by inattention, impulsivity, and/or hyperactivity in children and adults. Putative environmental risk factors for ADHD include toxin and prenatal smoke exposure, low socioeconomic status, and parental marital instability and discord. Genetic associations with ADHD have been found in the dopaminergic, serotonergic, and noradrenergic neurotransmitter systems, but findings are inconsistent across studies. Herein, we review studies of gene-environment interactions for ADHD to better understand how genetic and environmental risk factors may contribute to the disorder in a nonindependent fashion, which may account in part for the inconsistent findings on genetic associations. Although evidence of interactions between prenatal substance exposure and the dopamine genes DAT1 and DRD4 was found, findings across studies have been mixed. We discuss these findings and the future directions and limitations of current gene-environment research.

Choline transporter gene variation is associated with attention-deficit hyperactivity disorder

The neurotransmitter acetylcholine (ACh) plays a critical role in brain circuits mediating motor control, attention, learning and memory. Cholinergic dysfunction is associated with multiple brain disorders including Alzheimer’s Disease, addiction, schizophrenia and Attention-Deficit Hyperactivity Disorder (ADHD). The presynaptic choline transporter (CHT, SLC5A7) is the major, rate-limiting determinant of ACh production in the brain and periphery and is consequently upregulated during tasks that require sustained attention. Given the contribution of central cholinergic circuits to the control of movement and attention, we hypothesized that functional CHT gene variants might impact risk for ADHD. We performed a case-control study, followed by family-based association tests on a separate cohort, of two purportedly functional CHT polymorphisms (coding variant Ile89Val (rs1013940) and a genomic SNP 3’ of the CHT gene (rs333229), affording both a replication sample and opportunities to reduce potential population stratification biases. Initial genotyping of pediatric ADHD subjects for two purportedly functional CHT alleles revealed a 2–3 fold elevation of the Val89 allele (n = 100; P = 0.02) relative to healthy controls, as well as a significant decrease of the 3’SNP minor allele in Caucasian male subjects (n = 60; P = 0.004). In family based association tests, we found significant overtransmission of the Val89 variant to children with a Combined subtype diagnosis (OR = 3.16; P = 0.01), with an increased Odds Ratio for a haplotype comprising both minor alleles. These studies show evidence of cholinergic deficits in ADHD, particularly for subjects with the Combined subtype, and, if replicated, may encourage further consideration of cholinergic agonist therapy in the disorder.

Population density and youth antisocial behavior

Theoretical models concerning how neighborhood contexts adversely influence juvenile antisocial behavior frequently focus on urban neighborhoods; however, previous studies comparing urban and rural areas on the prevalence of youth antisocial behavior have yielded mixed results. The current study uses longitudinal data on the offspring of a nationally representative sample of mothers (N = 4,886) in the US. There was no relation between density and mother-reported child conduct problems across ages 4-13 years, but youth living in areas of greater population density exhibited more youth self-reported delinquency across 10-17 years. Families often moved to counties with greater or lesser population density, but longitudinal analyses treating population density as a time-varying covariate did not support the hypothesis that living in densely populated counties influenced youth delinquency. Rather, the association between population density and delinquency appears to be due to unmeasured selection variables that differ between families who live in more or less densely populated counties.

Maternal age at childbirth and offspring disruptive behaviors: testing the causal hypothesis

BACKGROUND

Recent studies suggest that the association between maternal age at childbearing (MAC) and children's disruptive behaviors is the result of family factors that are confounded with both variables, rather than a casual effect of environmental factors specifically related to MAC. These studies, however, relied on restricted samples and did not use the strongest approach to test causal influences.

METHODS

Using data on 9,171 4-9-year-old and 6,592 10-13-year-old offspring of women from a nationally representative sample of US households, we conducted sibling-comparison analyses. The analyses ruled out all genetic factors that could confound the association, as well as all environmental confounds that differ between unrelated nuclear families, providing a strong test of the causal hypothesis that the environments of children born at different maternal ages influence mother- and self-reported disruptive behaviors.

RESULTS

When these genetic and environmental confounds were ruled out as alternative explanations, the relation between environments within nuclear families specifically associated with MAC and disruptive behaviors was robust, with the association being stronger for second- and third-born children.

CONCLUSIONS

Environmental factors specifically associated with early MAC within nuclear families account for increased risk of offspring disruptive behaviors, especially in later-born children.

A quasi-experimental analysis of the association between family income and offspring conduct problems

The study presents a quasi-experimental analysis of data on 9,194 offspring (ages 4-11 years old) of women from a nationally representative U.S. sample of households to test the causal hypotheses about the association between family income and childhood conduct problems (CPs). Comparison of unrelated individuals in the sample indicated a robust inverse association, with the relation being larger at higher levels of income and for male offspring, even when statistical covariates were included to account for measured confounds that distinguish different families. Offspring also were compared to their siblings and cousins who were exposed to different levels of family income in childhood to rule out unmeasured environmental and genetic factors confounded with family income as explanations for the association. In these within-family analyses, boys exposed to lower family income still exhibited significantly higher levels of CPs. When considered in the context of previous studies using different designs, these results support the inference that family income influences CPs, particularly in males, through causal environmental processes specifically related to earnings within the nuclear family.

SNP discovery and haplotype analysis in the segmentally duplicated DRD5 coding region

The dopamine receptor 5 gene (DRD5) holds much promise as a candidate locus for contributing to neuropsychiatric disorders and other diseases influenced by the dopaminergic system, as well as having potential to affect normal behavioral variation. However, detailed analyses of this gene have been complicated by its location within a segmentally duplicated chromosomal region. Microsatellites and SNPs upstream from the coding region have been used for association studies, but we find, using bioinformatics resources, that these markers all lie within a previously unrecognized second segmental duplication (SD). In order to accurately analyze the DRD5 locus for polymorphisms in the absence of contaminating pseudogene sequences, we developed a fast and reliable method for sequence analysis and genotyping within the DRD5 coding region. We employed restriction enzyme digestion of genomic DNA to eliminate the pseudogenes prior to PCR amplification of the functional gene. This approach allowed us to determine the DRD5 haplotype structure using 31 trios and to reveal additional rare variants in 171 unrelated individuals. We clarify the inconsistencies and errors of the recorded SNPs in dbSNP and HapMap and illustrate the importance of using caution when choosing SNPs in regions of suspected duplications. The simple and relatively inexpensive method presented herein allows for convenient analysis of sequence variation in DRD5 and can be easily adapted to other duplicated genomic regions in order to obtain good quality sequence data.

Relations between multi-informant assessments of ADHD symptoms, DAT1, and DRD4

Researchers conducting candidate gene studies of attention-deficit/hyperactivity disorder (ADHD) typically obtain symptom ratings from multiple informants (i.e., mothers, fathers, and teachers) and use a psychologist's best estimate or a simple algorithm, such as taking the highest symptom ratings across informants, to construct diagnostic phenotypes for estimating association. Nonetheless, these methods have never been empirically validated in the context of a molecular genetic study. In the current study, the authors systematically evaluated several methods of operationalizing phenotypes and the resulting evidence for association between ADHD and the candidate genes: dopamine transporter gene (DAT1) and dopamine D4 receptor gene (DRD4). Use of symptom scores as continuous scales in regression analysis suggested that the combination of mother and teacher ratings yielded the strongest evidence for association between hyperactive-impulsive ADHD symptoms and DAT1 and between inattentive ADHD symptoms and DRD4. Teacher ratings alone were sufficient for evaluating the association between inattentive symptoms and DAT1. Further, this regression-based method consistently yielded stronger evidence for association among ADHD symptoms, DAT1, and DRD4 than did three simple algorithms (i.e., the and, or, and averaging rules). The implications of these results for future molecular genetic studies of ADHD are discussed.

Using epidemiologic methods to test hypotheses regarding causal influences on child and adolescent mental disorders

Epidemiology uses strong sampling methods and study designs to test refutable hypotheses regarding the causes of important health, mental health, and social outcomes. Epidemiologic methods are increasingly being used to move developmental psychopathology from studies that catalogue correlates of child and adolescent mental health to designs that can test rival hypotheses regarding causal genetic and environmental influences. A two-part strategy is proposed for the next phase of epidemiologic research. First, to facilitate the most informed tests of causal hypotheses, it is necessary to develop and test models of the structure of hypothesized genetic and environmental influences on mental health phenotypes. This will involve testing the related hypotheses that there are both (a) dimensions of psychopathology that are distinct in the sense of having at least some unique genetic and/or environmental influences, and (b) higher-order domains of correlated dimensions that are all apparently influenced in part by the same genetic and/or environmental factors. The resulting causal taxonomy would organize tests of causal hypotheses regarding both factors that may broadly increase risk for multiple dimensions of psychopathology and factors that may specifically increase risk for each individual dimension. Second, it is necessary to make greater use of a number of powerful epidemiologic designs that allow rigorous tests of rival hypotheses regarding genetic and environmental causes.

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.

Temperament and parenting during the first year of life predict future child conduct problems

Predictive associations between parenting and temperament during the first year of life and child conduct problems were assessed longitudinally in 1,863 offspring of a representative sample of women. Maternal ratings of infant fussiness, activity level, predictability, and positive affect each independently predicted maternal ratings of conduct problems during ages 4-13 years. Furthermore, a significant interaction indicated that infants who were both low in fussiness and high in predictability were at very low risk for future conduct problems. Fussiness was a stronger predictor of conduct problems in boys whereas fearfulness was a stronger predictor in girls. Conduct problems also were robustly predicted by low levels of early mother-report cognitive stimulation when infant temperament was controlled. Interviewer-rated maternal responsiveness was a robust predictor of conduct problems, but only among infants low in fearfulness. Spanking during infancy predicted slightly more severe conduct problems, but the prediction was moderated by infant fussiness and positive affect. Thus, individual differences in risk for mother-rated conduct problems across childhood are already partly evident in maternal ratings of temperament during the first year of life and are predicted by early parenting and parenting-by-temperament interactions.

Psychometric characteristics of a measure of emotional dispositions developed to test a developmental propensity model of conduct disorder

Lahey and Waldman proposed a developmental propensity model in which three dimensions of children's emotional dispositions are hypothesized to transact with the environment to influence risk for conduct disorder, heterogeneity in conduct disorder, and comorbidity with other disorders. To prepare for future tests of this model, a new measure of these dispositions was tested. Exploratory factor analysis of potential items was conducted in a sample of 1,358 participants 4 to 17 years of age. Confirmatory factor analyses then confirmed the three dispositional dimensions in a second sample of 2,063 pairs of 6- to 17-year-old twins. Caretaker ratings of the dispositional dimensions were associated as predicted with symptoms of conduct disorder and other psychopathology. In a third sample, caretaker ratings of each disposition correlated uniquely with relevant observational measures of child behavior and unintentional injuries. These findings provide initial support for the new dispositional measure.

Functional gene variation in the human norepinephrine transporter: association with attention deficit hyperactivity disorder

The norepinephrine (NE) transporter (NET) is responsible for the re-uptake of NE into presynaptic nerve terminals, thus critically regulating noradrenergic signaling and homeostasis. Since NE signaling contributes to diverse brain functions, we hypothesize that promoter variation within the human NET gene (solute carrier family 6, member 2; SLC6A2) may impact risk for NE-related disorders, including depression, attention deficit hyperactive disorder (ADHD), and autonomic dysfunction. In support of this, we recently found a functional polymorphism at -3081 position upstream of the transcription initiation site. This polymorphism displayed differential promoter function, which we showed could arise from recruitment of a transcriptional repressor. Further analyses identified Slug and Scratch as candidates involved in repression of SLC6A2 transcription generated by the -3081(T) allele. Moreover, we observed a significant association of the -3081(T) variant with ADHD. Altered transcription of SLC6A2 may therefore represent a novel risk factor for the development of ADHD.

Specification, testing, and interpretation of gene-by-measured-environment interaction models in the presence of gene-environment correlation

Purcell (Twin Res 5:554-571, 2002) proposed a bivariate biometric model for testing and quantifying the interaction between latent genetic influences and measured environments in the presence of gene-environment correlation. Purcell's model extends the Cholesky model to include gene-environment interaction. We examine a number of closely related alternative models that do not involve gene-environment interaction but which may fit the data as well as Purcell's model. Because failure to consider these alternatives could lead to spurious detection of gene-environment interaction, we propose alternative models for testing gene-environment interaction in the presence of gene-environment correlation, including one based on the correlated factors model. In addition, we note mathematical errors in the calculation of effect size via variance components in Purcell's model. We propose a statistical method for deriving and interpreting variance decompositions that are true to the fitted model.

Testing structural models of DSM-IV symptoms of common forms of child and adolescent psychopathology

Confirmatory factor analyses were conducted of Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) symptoms of common mental disorders derived from structured interviews of a representative sample of 4,049 twin children and adolescents and their adult caretakers. A dimensional model based on the assignment of symptoms to syndromes in DSM-IV fit better than alternative models, but some dimensions were highly correlated. Modest sex and age differences in factor loadings and correlations were found that suggest that the dimensions of psychopathology are stable across sex and age, but slightly more differentiated at older ages and in males. The dimensions of symptoms were found to be hierarchically organized within higher-order "externalizing" and "internalizing" dimensions, which accounted for much of their variance. Major depression and generalized anxiety disorder were substantially correlated with both the "externalizing" dimension and the "internalizing" dimension, however, suggesting the need to reconceptualize the nature of these higher-order dimensions.

Investigation of parent-of-origin effects in ADHD candidate genes

Attention deficit hyperactivity disorder (ADHD) is a common early-onset childhood disorder with a strong genetic component. Results from previous studies have suggested that there may be a parent-of-origin effect for ADHD candidate genes. In particular, a recent investigation identified a pattern of paternal over-transmission of risk alleles for nine ADHD candidate genes. We examined this phenomenon in a sample of 291 trios for five genes previously associated with ADHD (HTR1B, SNAP-25, DRD5, DAT1, and BDNF). Using a dense map of markers and two analytic methods in this relatively large family-based sample, we do not find any evidence for significant paternal over-transmission of risk alleles in these candidate loci. Thus, we conclude that a substantial parent-of-origin effect is unlikely for these leading ADHD candidate genes.

Sex differences in the causes of self-reported adolescent delinquency

Sex differences in the causes of self-reported adolescent delinquency were examined in full and half siblings born to a nationally representative sample of women in the United States. Qualitative sex differences in the genes that influence delinquency were not detected. Similarly, the proportions of variance in both aggressive and nonaggressive delinquency attributable to genetic and environmental influences did not differ significantly between girls and boys. Nonetheless, total variance in delinquency was greater among boys, and a scalar sex-differences model suggested that genetic and environmental influences on delinquency have less effect on population variation in delinquency among girls. Similarly, a test of the polygenic multiple threshold model suggested that girls require greater causal liability for the expression of delinquency than boys.

Testing descriptive hypotheses regarding sex differences in the development of conduct problems and delinquency

Accurate descriptions of sex differences in the development of childhood conduct problems and adolescent delinquency will inform theories of their causes in fundamentally important ways. Using data on 4,572 offspring of a national sample of women, we tested descriptive hypotheses regarding sex differences. As predicted, the magnitude of sex differences varied with age, suggesting that multiple processes differentially influence levels of these behaviors in females and males across development. During childhood, boys scored lower on measures of cognitive ability and exhibited lower sociability and compliance and greater hyperactivity, oppositional behavior, and conduct problems. Most of these variables were associated with childhood conduct problems and adolescent delinquency equally in females and males, but maternal delinquency and early childhood sociability were correlated more strongly with childhood conduct problems in males and childhood compliance predicted adolescent delinquency more strongly in females. Both sexes exhibited both childhood-onset and adolescent-onset trajectories of delinquency. Although more males followed a childhood-onset trajectory, there were few sex differences in the early childhood risk correlates of either delinquency trajectory.

A polymorphism in the norepinephrine transporter gene alters promoter activity and is associated with attention-deficit hyperactivity disorder

The norepinephrine transporter critically regulates both neurotransmission and homeostasis of norepinephrine in the nervous system. In this study, we report a previously uncharacterized and common A/T polymorphism at -3081 upstream of the transcription initiation site of the human norepinephrine transporter gene [solute carrier family 6, member 2 (SLC6A2)]. Using both homologous and heterologous promoter-reporter constructs, we found that the -3081(T) allele significantly decreases promoter function compared with the A allele. Interestingly, this T allele creates a new palindromic E2-box motif that interacts with Slug and Scratch, neural-expressed transcriptional repressors binding to the E2-box motif. We also found that both Slug and Scratch repress the SLC6A2 promoter activity only when it contains the T allele. Finally, we observed a significant association between the -3081(A/T) polymorphism and attention-deficit hyperactivity disorder (ADHD), suggesting that anomalous transcription factor-based repression of SLC6A2 may increase risk for the development of attention-deficit hyperactivity disorder and other neuropsychiatric diseases.

The adrenergic receptor alpha-2A gene (ADRA2A) and neuropsychological executive functions as putative endophenotypes for childhood ADHD

There is resurgent interest in the psychiatric literature in endophenotypes, variables thought to more strongly reflect the effects of candidate genes than do manifest disorders. In a sample of 176 children with attention deficit hyperactivity disorder (ADHD) and 52 of their siblings, we examined the validity of several putative endophenotypes for ADHD that represent commonly used clinical measures of multiple cognitive/neuropsychological domains of executive functions (EFs). We review their distributional normality, their relations to ADHD symptoms in probands and unaffected siblings relative to nonADHD controls, and their correlation in siblings. We also tested theEF measures' associations with the ADRA2A gene and whether they mediated or moderated the associations between ADHD and ADRA2A. Several EF measures showed association with ADRA2A, as well as moderation, but not mediation, of its association with ADHD. Implications of the results for evaluating the validity and utility of putative endophenotype measures and for finding candidate gene effects on ADHD are discussed.

The genetics of attention deficit hyperactivity disorder

Over the past 15 years, considerable progress has been made in understanding the etiology of childhood Attention Deficit Hyperactivity Disorder (ADHD), largely due to the publication of numerous twin studies which are consistent in suggesting substantial genetic influences (i.e., heritabilities ranging from 60% to 90%), non-shared environmental influences that are small-to-moderate in magnitude (i.e., ranging from 10% to 40%), and little-to-no shared environmental influences. Following from these quantitative genetic findings, numerous molecular genetic studies of association and linkage between ADHD and a variety of candidate genes have been conducted during the past 10 years. The majority of the candidate genes studied underlie various facets of the dopamine, norepinephrine, and serotonin neurotransmitter systems, although the etiological role of candidate genes outside of neurotransmitter systems (e.g., involved in various aspects of brain and nervous system development) have also been examined. In this paper, we review recent findings from candidate gene studies of childhood ADHD and highlight those candidate genes for which associations are most replicable and which thus appear most promising. We conclude with a consideration of some of the emerging themes that will be important in future studies of the genetics of ADHD.

Improved association analyses of disease subtypes in case-parent triads

The sampling of case-parent triads is an appealing strategy for conducting association analyses of complex diseases. In certain situations, one may have interest in using the triads to identify genetic variants that are associated with a specific subtype of disease, perhaps related to a characteristic cluster of symptoms. A straightforward strategy for conducting such a subtype analysis would be to analyze only those triads with the subtype of interest. While such a strategy is valid, we show that triads without the subtype of interest can provide additional genetic information that increases power to detect association with the subtype of interest. We incorporate this additional information using a likelihood-based framework that permits flexible modeling and estimation of allelic effects on disease subtypes and also allows for missing parental data. Using simulated data under a variety of genetic models, we show that our proposed association test consistently outperforms association tests that only analyze triads with the subtype of interest. We also apply our method to a triad study of attention-deficit hyperactivity disorder and identify a genetic variant in the dopamine transporter gene that is associated with a subtype characterized by extreme levels of both inattentive and hyperactive-impulsive symptoms.