aged 5 years that found that the effect of physical maltreatment increased the risk of conduct problems by 24% in children at high genetic risk, but by only 2% in children at low genetic risk [65]. The Minnesota Twin Family Study also showed that at age 17 years, genetic factors become more important as predictors of externalizing disorders, including substance abuse, in the context of environmental adversity [66]. For a comprehensive review of other studies of inferred genetic risk, see the article by Young-Wolff et al. [67•].
