Familial transmission and heritability of childhood disruptive disorders

Abstract

Objective: There is substantial evidence of a link between parental substance use disorders and antisocial behavior and childhood disruptive disorders in offspring, but it is unclear whether this transmission is specific to particular disorders or if a general liability accounts for familial resemblance. The authors examined whether the association between parental externalizing disorders and childhood disruptive disorders in preadolescent offspring is a result of the transmission of general or disorder-specific liabilities and estimated the genetic and environmental contributions to variation in these general and specific liability indicators.

Method: Participants were 1,069 families consisting of 11-year-old twins and their biological mother and father. Structural equation modeling was used to simultaneously estimate the general and specific transmission effects of four parental externalizing disorders (conduct disorder, adult antisocial behavior, alcohol dependence, and drug dependence) on childhood disruptive disorders (attention deficit hyperactivity disorder, conduct disorder, and oppositional defiant disorder).

Results: Parent-child resemblance was accounted for by the transmission of a general liability to externalizing disorders, and this general liability was highly heritable. Specific effects were also detected, but for sibling rather than parental transmission. Specific genetic and nonshared environmental effects were detected for each childhood disruptive disorder, but only conduct disorder exhibited a significant shared environmental effect.

Conclusions: A highly heritable general liability accounts for the parent-child transmission of externalizing psychopathology from parents to their preadolescent offspring. This general liability should be a focus of research for both etiology and intervention.

Figure 1. Final Model for General and Specific Transmission Effects

Note: All path coefficients in the figure are standardized. All paths presented in the figure are significant, p < .01. The latent externalizing (EXT) variables represent the general liability factors common among the 4 diagnoses for parents and 3 disorders for offspring. The circular blank latent variables associated with each disorder are the residual variances and represent liability factors that are specific to the disorder or unaccounted for by the general EXT liability factor. Double-headed arrows linking mother and father EXT to twin A and twin B EXT represent the general transmission effect for the 4 disorders. All parent-to-offspring effects were constrained to be equal, as model-fitting results indicated that there was not a statistically significant difference in the strength of maternal and paternal transmission. The double-headed arrow that links twin A and twin B EXT indexes monozygotic/dizygotic twin similarity for the general liability to the 3 disorders. The double-headed arrows linking the residual variances of ADHD, conduct disorder, and oppositional defiant disorder across members of the twin pair represent disorder-specific liabilities that increase sibling similarity but that are independent of the general EXT liability. AAB = Adult Antisocial Behavior; CD = Conduct disorder; ALD = Alcohol Dependence; DD = Drug Dependence; ADHD = Attention-Deficit Hyperactive Disorder; ODD = Oppositional Defiant Disorder; EXT-P = Externalizing factor for parents; EXT-O = Externalizing factor for offspring.

Figure 2. ACE Model for Childhood Disruptive Disorders

Note: Path coefficients and factor loadings are standardized and 95% confidence intervals are presented in parentheses beneath each coefficient. All coefficients whose CI does not include zero are significant. The percentage of variance accounted for by a given variable in another variable can be determined by squaring the path coefficient on the path connecting the first with the second variable. The sum of all the squared loadings (effects from the general EXT factor as well as the specific ACE loadings) equals 1. The total effect can be calculated by summing the general effect (squared factor loading for a given disorder multiplied by the squared A, C, or E path coefficient on EXT) and the specific effect (squared A, C, or E specific effect on a given disorder). Using CD as an example, h² = general [(.81)² × (.82)²] + specific [(.31)²] = .54. A = additive genetic effects; C = shared environmental effects; E = nonshared environmental effects; ADHD = Attention deficit/hyperactivity disorder; CD = conduct disorder; ODD = oppositional defiant disorder; EXT-O = Externalizing factor for offspring.