Family Aggregation of Substance Use Disorders: Substance Specific, Nonspecific, and Intrafamilial Sources of Risk.

Objective: The primary aim of this investigation was to evaluate substance-specific and nonspecific associations between parental and sibling histories of alcohol, cannabis, amphetamine, and hallucinogen use disorders with proband risk for these conditions. A second aim was to evaluate whether the specificity of substance use disorder (SUD) risk to probands varied by family member (i.e., father, mother, and any sibling).

Method: Lifetime SUD diagnostic data for this family-based investigation were derived from semistructured interviews of community residents. Participants were an age-based cohort (probands), selected at random during adolescence and followed longitudinally until age 30, and their first-degree family members (n = 803 probands and families).

Results: Findings generally supported substance-specific and nonspecific forms of familial risk related to a particular type of SUD in probands. Family-based alcohol use disorder (AUD) demonstrated the greatest degree of risk specificity of any substance category, in that no other family SUD category predicted proband AUD. Family-based AUD, however, was also the most consistent nonspecific predictor of nonalcohol forms of SUD among probands. Among family members, the most consistent unique effects associated with a substance-specific risk to probands were observed for siblings.

Conclusions: Findings support both the generality and specificity of risk associated with the abuse of or dependence on specific substances within families and highlight the impact of siblings on SUD risk to other siblings. Study findings underscore the need for a better understanding of malleable family-based factors that promote and reduce SUD risk among members.