Antisocial behavior and substance use disorders have serious consequences for youth, their families, and costs to society in terms of education, mental health and health treatment, and criminal justice system involvement. Evidence has shown that genetic and environmental factors contribute to the development of these problems, although a clearer understanding of how genetics and environmental factors work together is warranted.
The Minnesota Twin Family Study is an ongoing longitudinal study of Minnesota same-sex twins. For this report, psychologists at the University of Minnesota assessed 1,315 adolescent twin pairs on several environmental factors: academic achievement and engagement, peer affiliation, parent-child relationships, and stressful life events. Data were collected through multi-modal means, including structured clinical interviews, self-report questionnaires, and teacher rating forms. The researchers examined antisocial behavior and substance use disorders at age 17.
Results and Conclusions
The study’s main conclusion involved the interaction of genetic and environmental risk. Specifically, the greater the environmental stress, the more likely genetic risk was exacerbated; the converse was also true: environments that were more stable and structured suppressed risk. Environmental stress without genetic risk does not seem to result in antisocial behaviors and substance use disorders.
This study has a number of strengths, including its large sample size and the combined examination of genetic and environmental factors. The implication is that environmental structure and stability can constrain genetic risk for externalizing disorders, although it is also recognized that those with genetic risk may encounter environmental adversity (e.g.., they will tend to seek out negative peers who will, in turn, exert a negative influence on them). Apparently, however, both genetic and environmental risk need to be present in order for problems to develop in late adolescence.
Hicks, B., South, S., Dirago, A., Iacono, W., & McGue, M. (2009). Environmental adversity and increasing genetic risk for externalizing disorders. Archives of General Psychiatry, 66, 640-648.