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 fo r substance use disorders (SUDs) among children of alcoholics may be the re aring 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 estimat ed independently of genetic influences through assessment of adoptees raise d 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 c ommunity-based National Longitudinal Alcohol Epidemiologic Survey (NLAES). Results: Rearing by an alcoholic adoptive mother was associated with increa sed DSM-IV alcohol abuse. Rearing by an alcoholic adoptive father was predi ctive of adoptees' illicit drug use, as well as DSM-IV drug dependence. Rea ring by an alcoholic stepfather was predictive of stepchild DSM-IV alcohol abuse, illicit drug use, and drug dependence, whereas an alcoholic stepmoth er was associated with increased illicit drug use in the stepchild. Alcohol ism 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 tha t expected based on the additive effects of each alcoholic parent. Conclusions: Rearing by an alcoholic parent had a greater influence on alco hol abuse by offspring than on alcohol dependence. The increased risk of pr oband illicit drug use and drug dependence associated with paternal alcohol ism suggested nonspecificity of environmental transmission. Both maternal a nd paternal cultural transmission effects influenced offspring SUDs.