Environmental adversity and increasing genetic risk for externalizing disorders.

CONTEXT: Studies of gene-environment interplay in the development of psychiatric and substance use disorders are rapidly accumulating. However, few attempts have been made to integrate findings and to articulate general mechanisms of gene-environment influence in the emergence of psychopathology.
OBJECTIVE: To identify patterns of gene-environment interplay between externalizing disorders (antisocial behavior and substance use) and several environmental risk factors.
DESIGN: We used quantitative genetic models to examine how genetic and environmental risk for externalizing disorders changes as a function of environmental context.
SETTING: Participants were recruited from the community and took part in a daylong assessment at a university laboratory. PARTICIPANTS: The sample consisted of 1315 male and female twin pairs participating in the assessment of the Minnesota Twin Family Study at age 17 years. MAIN OUTCOME MEASURES: Multiple measures and informants were used to construct a composite of externalizing disorders and composite measures of 6 environmental risk factors, including academic achievement and engagement, antisocial and prosocial peer affiliations, mother-child and father-child relationship problems, and stressful life events.
RESULTS: A significant gene x environment interaction was detected between each environmental risk factor and externalizing such that greater environmental adversity was associated with increased genetic risk for externalizing.
CONCLUSIONS: In the context of environmental adversity, genetic factors become more important in the etiology of externalizing disorders. The consistency of the results further suggests a general mechanism of environmental influence on externalizing disorders regardless of the specific form of the environmental risk.