Familial influences on conduct disorder reflect 2 genetic factors and 1 shared environmental factor.

CONTEXT: Prior studies suggest that antisocial behavior in childhood and adolescence reflects multiple symptomatic dimensions. However, to our knowledge, no prior study has evaluated the underlying nature of the etiologic influences contributing to conduct disorder (CD) symptoms as defined in the DSM.
OBJECTIVE: To determine the structure of genetic and environmental risk factors for CD.
DESIGN: Population-based twin registry.
SETTING: Virginia. PARTICIPANTS: Two thousand seven hundred sixty-nine members of male-male twin pairs from the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders. MAIN OUTCOME MEASURE: Retrospective self-reported symptoms of CD.
RESULTS: The best-fitting multivariate twin model included 2 genetic factors, 1 shared environmental common factor, and 1 nonshared environmental common factor, along with criterion-specific genetic and nonshared environmental effects. The CD criteria with the strongest loadings on the 2 genetic factors were, respectively, those reflecting rule breaking (eg, playing hooky) and overt aggressive acts (eg, hurting people). The shared environmental common factor had salient loadings on a distinct set of criteria reflecting covert delinquent acts (eg, stealing and hurting animals). Loadings on the single nonshared environmental common factor were more uniform and less selective. Scores on the 3 familial CD factors were differentially associated with a range of personality, psychopathology, and demographic factors.
CONCLUSIONS: From a genetic perspective, the DSM criteria for CD do not reflect a single dimension of liability. The familial risk to CD is composed of 2 discrete dimensions of genetic risk, reflecting rule breaking and overt aggression, and 1 dimension of shared environmental risk, reflecting covert delinquency. These 3 familial factors differ meaningfully in their association with a range of relevant validators.