The moderating effect of parental illicit substance use disorders on the relation between adolescent depression and subsequent illicit substance use disorders

Background: Previous research has demonstrated that depression and family history of illicit substance use disorders (ISUDs) are risk factors for the development of ISUDs. However, no study to date has examined whether these risk factors interact to predict onset. In addition, history of parental and sibling ISUDs have been identified as risk factors almost exclusively in healthy individuals and thus, it is unknown whether they confer unique risk among adolescents with a history of depression. Methods: The current study examined these questions using data from the Oregon Adolescent Depression Project (OADP). DSM diagnoses of probands were assessed during 4-waves, first in adolescence (ages 14-18) and subsequently up until age 30. Lifetime DSM diagnoses of ISUDs in biological mothers, fathers, and siblings were obtained. Results: Proportional hazards model analyses indicated that there was a significant depression by parental ISUDs interaction. Among probands with parental ISUDs (and not among those without parental ISUDs), depression in adolescence was significantly associated with a shorter time to develop an ISUD. Sibling ISUDs were not associated with onset and did not interact with adolescent depression. Conclusion: Prevention and intervention efforts targeted at this particularly at-risk group may be effective.