Environmental transmission of DSM-IV substance use disorders in adoptive and step families

Background: One factor contributing to the 3- to 5-fold increase in risk for substance use disorders (SUDs) among children of alcoholics may be the rearing environment. These influences may include availability of substances, modeling of SUDs, inadequate parenting, or other factors. The contribution of parental environmental influences on offspring with SUDs may be estimated independently of genetic influences through assessment of adoptees raised by nonbiological parents. Methods: Relative risk of SUDs was assessed in adult adoptees (N = 442) of alcoholic and nonalcoholic adoptive parents as well as in stepchildren (N = 1859) with alcoholic or nonalcoholic stepfathers who participated in the community-based National Longitudinal Alcohol Epidemiologic Survey (NLAES). Results: Rearing by an alcoholic adoptive mother was associated with increased DSM-IV alcohol abuse. Rearing by an alcoholic adoptive father was predictive of adoptees' illicit drug use, as well as DSM-IV drug dependence. Rearing by an alcoholic stepfather was predictive of stepchild DSM-IV alcohol abuse, illicit drug use, and drug dependence, whereas an alcoholic stepmother was associated with increased illicit drug use in the stepchild. Alcoholism in adoptive parents or step parents did not increase risk for offspring DSM-IV alcohol dependence. In both adoptive and biological families, there was a subadditive interaction of mother by father alcoholism such that the rate of substance abuse when both parents were alcoholic was less than that expected based on the additive effects of each alcoholic parent. Conclusions: Rearing by an alcoholic parent had a greater influence on alcohol abuse by offspring than on alcohol dependence. The increased risk of proband illicit drug use and drug dependence associated with paternal alcoholism suggested nonspecificity of environmental transmission. Both maternal and paternal cultural transmission effects influenced offspring SUDs.