Dr. Keyes Replies

To the Editor: We certainly agree with Dr. Harvey that many environmental factors may influence adolescent disinhibited behavior, including neglect or abuse in the home as well as psychiatric disorders in the parents. We also believe that adoption designs offer an especially sensitive test for the presence of family-level environmental influences. That is, studying adoptive families allows researchers to control for genetic confounding when examining between-family environmental effects. Our study presented evidence for one environmentally mediated pathway by which parental smoking increased risk for substance use in adolescent offspring. Another study, using the same sample, demonstrated that maternal depression represented an environmental liability for major depression and disruptive behavior disorders in adolescent offspring (1) . We hope that these results will encourage further investigation of environmental influences on adolescent behavior within the context of a genetically informative design.