Understanding the Covariation Among Childhood Externalizing Symptoms: Genetic and Environmental Influences on Conduct Disorder,Attention Deficit Hyperactivity Disorder,and Oppositional Defiant Disorder Symptoms

Conduct disorder (CD), attention deficit hyperactivity disorder (ADHD), and oppositional defiant disorder (ODD) are common childhood externalizing disorders that frequently co-occur. However, the causes of their comorbidity are not well understood. To address that question, we analyzed data from > 600 Finnish twin pairs, who completed standardized interviews at age 14. Behavior genetic methods were used to examine how genetic/environmental factors contribute to each disorders symptoms and to their covariation. We found significant genetic effects on each disorder with only modest evidence of shared environmental influences. Our data suggest the comorbidity among CD, ADHD, and ODD is primarily explained by shared genetic influences; however, each disorder was also under unique genetic influence, supporting the distinction of each disorder.     

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. This study was funded by NIMH (R01 MH58354). Catherine Tuvblad was supported by post-doctoral stipends from the Swedish Council for Working Life and Social Research (Project 2006-1501) and the Sweden-America Foundation. Adrian Raine was supported by NIMH (Independent Scientist Award K02 MH01114-08). We thank the Southern California Twin Project staff for their assistance in collecting data, and the twins and their families for their participation.     

Do Genetic Factors Explain the Links Between Callous-Unemotional,Attention Hyperactivity and Oppositional Defiant Problems in Toddlers?

Research demonstrates that callous-unemotional (CU) behaviors, Attention Deficit Hyperactivity Disorder (ADHD) and Oppositional Defiant Problems (ODD) are related, but little is known about the sources of covariation among the three externalizing behaviors. The present study looked at genetic and environmental links between all three behavioral domains in twins at ages 2 and 3 years (MZ = 145, DZ = 169), a time when CU behaviors are beginning to emerge. CU, ADHD, and ODD behaviors as assessed using the Child Behavior Checklist 1.5–5 (Achenbach and Rescorla 2000) were strongly interrelated at both ages. Genetic factors primarily explained the covariation among the three behavioral domains via a common externalizing factor; however, there were also genetic factors unique to each behavior. Furthermore, the majority of nonshared environmental influences on each externalizing behavior were behavior-specific. The heritable externalizing factor was highly stable across age, largely due to genetic factors shared across ages 2 and 3 years. Despite their extensive phenotypic and genetic overlap, CU, ADHD, and ODD behaviors have unique genetic and nonshared environmental influences as early as toddlerhood. This supports phenotypic research showing that the three are related but distinct constructs in very young children.     

Genetic and Environmental Contributions to Common Psychopathologies of Childhood and Adolescence: A Study of Twins and Their Siblings

We report findings based on analyses of self-reports of six common adolescent psychopathologies (attention deficit/hyperactivity disorder, ADHD; conduct disorder, CD; oppositional defiant disorder, ODD; generalized anxiety disorder, GAD; separation anxiety disorder, SAD; and major depressive disorder, MDD) in a sample of 1,162 male and female adolescent (12–19 years) twin pairs and 426 siblings. Prevalence statistics for past year and lifetime reports confirm differences between genders for CD, GAD, SAD, and MDD, and a lack of differences between twins and their non-twin siblings. Biometrical modeling was conducted to ascertain the relative influences of genes, and shared and non-shared environments contributing to these disorders. A more robust estimate of these parameters was obtained by including non-twin siblings. Age-specific thresholds were integrated into the analyses to appropriately model the developmental patterns of behavior. We found evidence for both genetic and non-shared environmental influences for all disorders. Shared environmental influences also seem to be important for MDD and lifetime GAD.     

Unintentional Injury Risk in Children with Externalizing Behavior Disorders at Summer Camp

Children with externalizing behavior disorders such as attention-deficit/hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), and conduct disorder (CD) have greatly increased risk of unintentional injury, but it is unclear what mechanisms are responsible for that increased risk. This study followed 22 children participating in a summer camp for children with ADHD. Injury incidents were recorded daily and a set of primary symptoms of behavioral disorders were recorded at 15-min intervals over the course of the 6-week summer camp experience (roughly 300 h of observing each child). We predicted symptoms of ODD and CD would be more strongly related to injury incidence than symptoms of ADHD. Results from univariate Poisson regression models confirmed our prediction. Symptoms of ODD and CD—violations and intentional aggression in particular—were related to injury incidence but symptoms of ADHD were not. This finding is consistent with a growing body of evidence that oppositional, noncompliant, and aggressive behavior patterns might be primarily responsible for increased risk for injury among children with externalizing behavior disorders. Thanks to Sylvie Mrug, Peter Winslett, and the other staff members of the STP camp for their cooperation.     

The role of a lifetime history of oppositional defiant and conduct disorders in adults with ADHD: implications for clinical practice

IntroductionAttention-deficit/hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), and conduct disorder (CD) are frequently co-occurring disorders in children and adolescents. However, their clinical status among adults is still under discussion. This study analyzes how the current clinical presentation of adult ADHD might be influenced by a lifetime history of CD and ODD. METHODS: We compared three groups of patients: ADHD without history of CD/ODD (n = 178), ADHD + history of ODD (n = 184), and ADHD + history of CD (n = 96). RESULTS: A history of CD (and to a lower extent ODD) is associated with a more severe and externalizing profile.ConclusionPast CD and ODD entail a significant negative mental health impact on persistent ADHD, reinforcing the importance of actively assessing the developmental history of adult ADHD patients.     

Exploring how symptoms of attention-deficit/hyperactivity disorder are related to reading and mathematics performance: general genes, general environments

Children with attention-deficit/hyperactivity disorder (ADHD) tend to perform more poorly on tests of reading and mathematical performance than their typical peers. Quantitative genetic analyses allow for a better understanding of the etiology of ADHD and reading and mathematics outcomes, by examining their common and unique genetic and environmental influences. Analyses were conducted on a sample 271 pairs of 10-year-old monozygotic and dizygotic twins drawn from the Western Reserve Reading and Mathematics Project. In general, the results suggested that the associations among ADHD symptoms, reading outcomes, and math outcomes were influenced by both general genetic and general shared-environment factors. The analyses also suggested significant independent genetic effects for ADHD symptoms. The results imply that differing etiological factors underlie the relationships among ADHD and reading and mathematics performance. It appears that both genetic and common family or school environments link ADHD with academic performance.     

Adolescents with attention deficit hyperactivity disorder: Mother-adolescent interactions,family beliefs and conflicts,and maternal psychopathology

A group of 83 adolescents with attention deficit hyperactivity disorder (ADHD) were subdivided into those with ADHD alone (n = 27) and those with ADHD and oppositional defiant disorder (ADHD/ODD, n = 56). They were compared to each other and a community control group (n = 77) on measures of family conflicts, family beliefs, maternal adjustment, and observations of mother-adolescent interactions during both a neutral and conflict discussion. Both ADHD groups had more topics on which there was conflict and more angry conflicts at home than control adolescents on parent reports. Only the ADHD/ODD adolescents reported more such conflicts, endorsed more extreme and unreasonable beliefs about their parent-teen relations, and demonstrated greater negative interactions during a neutral discussion than the control teenagers. Similarly, only mothers of the ADHD/ODD teens displayed greater negative interactions during a neutral discussion, more extreme and unreasonable beliefs about their parent-teen relations, greater personal distress, and less satisfaction in their marriages than the mothers in the control group. Most findings for the ADHD only group were between the control group and the group with mixed ADHD/ODD but did not differ from either group. Results imply that it is the combination of ODD symptoms with those of ADHD that is associated with the greater-than-normal conflicts, anger, poor communications, unreasonable beliefs, and negative interactive styles seen in ADHD adolescents. These same characteristics typify their mothers' interactions as well such that both the adolescents' ODD symptoms and maternal psychological distress (hostility) make unique contributions to the degree of conflict and anger in the parent-teen relations of ADHD adolescents.     

Problem of item overlap between the psychopathy screening device and attention deficit hyperactivity disorder, oppositional defiant disorder, and conduct disorder rating scales

Content validity requires a clear definition of the construct of interest and the delineation of the construct from similar constructs. Content validity also requires that the items be representative of the construct as well as specific to the construct. An examination of the items on the Psychopathy Screening Device (PSD), a parent- and teacher-rating scale of childhood psychopathy, indicates significant overlap with the symptoms and associated features of attention deficit hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), and conduct disorder (CD). The failure of the PSD to have unique items results in poor discriminant validity with ADHD, ODD, and CD rating scales. More careful attention to content validation guidelines is required to develop a more useful measure of childhood psychopathy.     

Diagnostic conundrum of oppositional defiant disorder and conduct disorder

Evidence for a diagnostic distinction of oppositional defiant disorder (ODD) and conduct disorder (CD) is reviewed, and alternative conceptualizations and definitions for the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders are considered. Studies suggest that CD and ODD are strongly and developmentally related but clearly different. Factor analyses indicate that distinct covarying groups of ODD and CD symptoms can be identified, but certain symptoms relate to both (particularly mild aggression and lying). Age of onset for ODD is earlier than for most CD symptoms. Nearly all youths with CD have a history of ODD, but not all ODD cases progress to CD. The disorders demonstrate the same forms of parental psychopathology and family adversity but to a greater degree for CD than for ODD. Alternative conceptualizations for the disorders are presented for further study before the introduction of the DSM-IV.     

Negative Halo Effects in Parent Ratings of ADHD,ODD, and CD

Attention-deficit/hyperactivity disorder (ADHD), Oppositional Defiant Disorder (ODD), and Conduct Disorder (CD) are highly comorbid, with symptoms that share some similarities. The evidence-based diagnostic process for these disorders includes ratings from adults in the child’s life to assess behavior across settings, so it is important to understand how these raters think about potentially overlapping symptoms. Researchers have identified negative halo effects in ratings of ADHD and ODD symptoms, but ratings of CD have not been examined in these prior studies. Thus, the current study extended past research to examine negative halo effects in parent ratings of the predominantly hyperactive-impulsive presentation of ADHD (i.e., ADHD/HI), ODD, and CD. Parent participants read one of four vignettes that portrayed an 11-year-old boy displaying symptoms of ADHD/HI, ODD, CD, or typical development, and then completed a disruptive behavior scale. The general trend we found was that the presence of a relatively more severe disorder (i.e., CD) artificially inflated ratings of - or showed a negative halo effect for - the relatively less severe disorder (i.e., ADHD/HI), but with some nuance as discussed in the paper. These findings explain and validate how important it is that clinicians conduct evidence-based psychological assessments to decrease the chance of misdiagnosis.

     

Preschoolers at risk for attention-deficit hyperactivity disorder and oppositional defiant disorder: family,parenting, and behavioral correlates

This community study assigned 129 4-year-olds to groups at risk for attention deficit hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), both ADHD and ODD, or no problems. Mothers of children at risk for ODD reported more family dysfunction, felt less competent as parents, suggested fewer solutions to child behavior problems, demonstrated a less assertive approach to child management, and reported more child internalizing problems than did mothers of children not elevated on ODD symptoms. Mothers of children at risk for ADHD reported higher personal depression scores than did those of the non-ADHD subgroup. Children at risk for ADHD evidenced the most difficulties in school where teachers reported more social behavior, classroom management, and internalizing problems relative to other children not at risk for ADHD. When solving child management problems, mothers of children in all groups suggested twice as many controlling/negative management strategies as positive/preventive strategies. In addition, faced with oppositional and conduct problems, mothers of children in all groups increased controlling/negative suggestions and decreased positive/preventive suggestions. Mothers of girls at risk for ADHD, ODD, and ADHD/ODD gave more rewards per positive behavior than did mothers of boys.     

Searching for an environmental effect of parental alcoholism on offspring alcohol use disorder: a genetically informed study of children of alcoholics

The children-of-twins design was used to isolate a potentially causal environmental impact of having an alcoholic parent on offspring alcohol use disorder, by an examination of whether the children of alcoholics were at a higher risk for alcohol use disorders than were the children of nonalcoholic parents, even after correlated familial factors were controlled. Participants were 1,224 male and female twins from 836 twin pairs selected from the Australian Twin Registry, 2,334 of the twins' 18-39-year-old offspring, and 983 spouses of the twins. Lifetime histories of Diagnostic and Statistical Manual of Mental Disorders (4th ed.) alcohol use disorders were obtained by structured, psychiatric, telephone interviews conducted individually with each of the family members. Comparisons of the offspring of twins who were discordant for alcoholism indicated that there was no longer a statistically significant difference between the children of alcoholics and the children of nonalcoholics after genetic and family environmental factors correlated with having an alcoholic parent were controlled. The results of this study suggest that the direct causal effect of being exposed to an alcoholic parent on offspring alcohol use disorder is modest at best.     

Problems in Psychiatric Genetic Research: A Reply to Faraone and Biederman

This article examines evidence cited in favor of the operation of genetic factors in attention-deficit hyperactivity disorder (ADHD). Like other psychiatric conditions, a belief in the genetic basis of ADHD is derived from the results of family, twin, and adoption studies. Because family studies are widely believed to be confounded by environmental factors, primary emphasis is placed on twin and adoption studies. ADHD twin studies depend on the validity of the equal environment assumption (EEA), which holds that the environments of identical (MZ) and fraternal (DZ) twins are the same. Here it is argued that however the EEA is defined, it cannot be accepted. Therefore, the greater similarity or concordance of MZ twins when compared to DZ twins is plausibly explained by environmental factors. Adoption studies constitute a third method for investigating the role of genetic factors in ADHD. It is argued that these studies are greatly flawed by factors including non blinded diagnoses and the failure to study the biological relatives of adoptees. After an examination of the total weight of evidence in favor of a genetic basis or predisposition for ADHD, it is concluded that a role for genetic factors is not supported and that future research should be directed toward psychosocial causes     

Evidence for a Multi-Dimensional Latent Structural Model of Externalizing Disorders

Strong associations between conduct disorder (CD), antisocial personality disorder (ASPD) and substance use disorders (SUD) seem to reflect a general vulnerability to externalizing behaviors. Recent studies have characterized this vulnerability on a continuous scale, rather than as distinct categories, suggesting that the revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) take into account the underlying continuum of externalizing behaviors. However, most of this research has not included measures of disorders that appear in childhood [e.g., attention-deficit/hyperactivity disorder (ADHD) or oppositional defiant disorder (ODD)], nor has it considered the full range of possibilities for the latent structure of externalizing behaviors, particularly factor mixture models, which allow for a latent factor to have both continuous and categorical dimensions. Finally, the majority of prior studies have not tested multidimensional models. Using lifetime diagnoses of externalizing disorders from participants in the Fast Track Project (n?=?715), we analyzed a series of latent variable models ranging from fully continuous factor models to fully categorical mixture models. Continuous models provided the best fit to the observed data and also suggested that a two-factor model of externalizing behavior, defined as (1) ODD+ADHD+CD and (2) SUD with adult antisocial behavior sharing common variance with both factors, was necessary to explain the covariation in externalizing disorders. The two-factor model of externalizing behavior was then replicated using a nationally representative sample drawn from the National Comorbidity Survey-Replication data (n?=?5,692). These results have important implications for the conceptualization of externalizing disorders in DSM-5.     

Passive-aggressive (negativistic) personality disorder: a population-based twin study

The objective of this study was to investigate the familial aggregation of passive aggressive personality disorder (PAPD), and explore issues regarding PAPD raised by the DSM-IV Personality Disorder Work Group. Two thousand seven hundred and ninety-four Norwegian twins from the population-based Norwegian Institute of Public Health Twin Panel were interviewed with the Structured Interview for DSM-IV Personality (SIDP-IV). Because of the rarity of the twins meeting full diagnostic criteria for PAPD a dimensional representation of the disorder was used for the analyses. Overlap with other axis II disorders was assessed by polychoric correlations, while familial aggregation was explored by structural equation twin models. Overlap was highest with paranoid (r = 0.52) and borderline personality disorder (r = 0.53), and lowest with schizoid (r = 0.26). Significant familial aggregation was found for PAPD. The twin correlations and parameter estimates in the full model indicated genetic and shared environmental effects for females, and only shared environmental effects for males, but the prevalence of endorsed PAPD criteria in this community sample was too low to permit us to conclude with confidence regarding the relative influence of genetic and shared environmental factors on the familial aggregation of PAPD.     

The Genetic Association Between ADHD Symptoms and Reading Difficulties: The Role of Inattentiveness and IQ

Previous studies have documented the primarily genetic aetiology for the stronger phenotypic covariance between reading disability and ADHD inattention symptoms, compared to hyperactivity-impulsivity symptoms. In this study, we examined to what extent this covariation could be attributed to “generalist genes” shared with general cognitive ability or to “specialist” genes which may specifically underlie processes linking inattention symptoms and reading difficulties. We used multivariate structural equation modeling on IQ, parent and teacher ADHD ratings and parent ratings on reading difficulties from a general population sample of 1312 twins aged 7.9–10.9 years. The covariance between reading difficulties and ADHD inattention symptoms was largely driven by genetic (45%) and child-specific environment (21%) factors not shared with IQ and hyperactivity-impulsivity; only 11% of the covariance was due to genetic effects common with IQ. Aetiological influences shared among all phenotypes explained 47% of the variance in reading difficulties. The current study, using a general population sample, extends previous findings by showing, first, that the shared genetic variability between reading difficulties and ADHD inattention symptoms is largely independent from genes contributing to general cognitive ability and, second, that child-specific environment factors, independent from IQ, also contribute to the covariation between reading difficulties and inattention symptoms.     

Evidence for the Trait-Impulsivity Etiological Model in a Clinical Sample: Bifactor Structure and Its Relation to Impairment and Environmental Risk

The trait-impulsivity etiological model assumes that a general factor (trait-impulsivity) underlies attention-deficit/hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), and other externalizing disorders. We investigated the plausibility of this assumption by testing the factor structure of ADHD and ODD in a bifactor framework for a clinical sample of 1420 children between 6 and 18 years of age (M = 9.99, SD = 3.34; 85% male). Further, the trait-impulsivity etiological model assumes that ODD emerges only if environmental risk factors are present. Our results support the validity of the trait-impulsivity etiological model, as they confirm that ADHD and ODD share a strong general factor of disruptive behavior (DB) in this clinical sample. Furthermore, unlike the subdimensions of ADHD, we found that the specific ODD factor explained as much true score variance as the general DB factor. This suggests that a common scale of ADHD and ODD may prove to be as important as a separate ODD subscale to assess externalizing problems in school-age children. However, all other subscales of ADHD may not explain sufficient true score variance once the impact of the general DB factor has been taken into consideration. In accordance with the trait-impulsivity model, we also showed that all factors, but predominantly the general factor and specific inattention factor, predicted parent-rated impairment, and that predominantly ODD and impulsivity are predicted by environmental risk factors.     

Sex differences in the genetic and environmental influences on childhood conduct disorder and adult antisocial behavior

Sex differences in the genetic and environmental influences on childhood conduct disorder and adult antisocial behavior were examined in a large community sample of 6,383 adult male, female, and opposite-sex twins. Retrospective reports of childhood conduct disorder (prior to 18 years of age) were obtained when participants were approximately 30 years old, and lifetime reports of adult antisocial behavior (antisocial behavior after 17 years of age) were obtained 8 years later. Results revealed that either the genetic or the shared environmental factors influencing childhood conduct disorder differed for males and females (i.e., a qualitative sex difference), but by adulthood, these sex-specific influences on antisocial behavior were no longer apparent. Further, genetic and environmental influences accounted for proportionally the same amount of variance in antisocial behavior for males and females in childhood and adulthood (i.e., there were no quantitative sex differences). Additionally, the stability of antisocial behavior from childhood to adulthood was slightly greater for males than females. Though familial factors accounted for more of the stability of antisocial behavior for males than females, genetic factors accounted for the majority of the covariation between childhood conduct disorder and adult antisocial behavior for both sexes. The genetic influences on adult antisocial behavior overlapped completely with the genetic influences on childhood conduct disorder for both males and females. Implications for future twin and molecular genetic studies are discussed.     

Suicidal Ideation, Depression, and Conduct Disorder in a Sample of Adolescent and Young Adult Twins

The co-occurrence of suicidal ideation, depression, and conduct disturbance is likely explained in part by correlated genetic and environmental risk factors. Little is known about the specific nature of these associations. Structured interviews on 2,814 twins from the Virginia Twin Study of Adolescent Behavioral Development (VTSABD) and Young Adult Follow-Up (YAFU) yielded data on symptoms of depression, conduct disorder, and adolescent and young adult suicidal ideation. Univariate analyses revealed that the familial aggregation for each trait was explained by a combination of additive genetic and shared environmental effects. Suicidal ideation in adolescence was explained in part by genetic influences, but predominantly accounted for by environmental factors. A mixture of genetic and shared environmental influences explained ideation occurring in young adulthood. Multivariate analyses revealed that there are genetic and shared environmental effects common to suicidal ideation, depression, and conduct disorder. The association between adolescent suicidal ideation and CD was attributable to the same genetic and environmental risk factors for depression. These findings underscore that prevention and intervention strategies should reflect the different underlying mechanisms involving depression and conduct disorder to assist in identifying adolescents at suicidal risk.