Genetic and environmental risk factors for the onset of drug use and problems in adoptees.

Applying survival analysis methodology to age-of-onset data from an adoption study (N = 196), we present evidence that risks for both drug use and drug problems (DSM abuse or dependence) are elevated when combined antisocial personality (ASP) and substance abuse is present in the same biological parent. It is increased not only in comparison to adoptees with no known biological risk, but also when compared to adoptees with a biological background for only substance problems or only ASP. Neither of these later groups showed a statistically higher risk when compared with controls. Among adoptees with recurrent drug use, adolescent aggressivity is also elevated when the combined substance abuse/ASP biological diathesis is present. Statistical control for aggressivity diminished but did not eliminate the predictive significance of the combined biological diathesis for drug problems. We also verify, using more refined methodology, our previous reports of gender and adverse adoptive environmental influences on drug-related outcomes in these subjects. We could not document a biology-environment interaction, but power to do so was rather low. We argue that the observed biological associations are broadly consistent with generalization to other substances of an alcoholism phenotype similar to Cloninger's Type II or Babor's Type B.