Family history density predicts long term substance use outcomes in an adolescent treatment sample

• Family history density predicted more total drinks and more marijuana use days.
• The risk associated with family history increases over time.
• Family history is a risk factor for poorer long-term treatment outcomes.

AimsThis study explored whether the density of family history (FH) of substance use disorders relates to post-treatment substance use outcomes in adolescents, with the primary aim of determining whether FH exerts a relatively stronger influence on longer-term outcomes.MethodThe present investigation examined adolescents (ages 12–18, n = 366) from two independent samples who were treated for alcohol/substance use disorder (ASUD) and re-assessed during the eight years following treatment with identical methodology. Primary substance use outcomes were assessed at 1, 2, 4, 6, and 8 years post-treatment and included total drinks, days using marijuana, and days using other drugs.ResultsIn hierarchical linear models there were significant FH density × linear time interactions for total drinks (z = 12.75, p < 0.001) and marijuana use days (z = 4.39, p < 0.001); greater FH density predicted more total drinks and more marijuana use days, with both associations becoming stronger over time. The increasing linkage between FH and other drug use was not significant over time.ConclusionsFindings are consistent with previous research indicating that the risk associated with FH increases over time, especially in relation to quantity/frequency measures of alcohol and marijuana use. By extending these findings to an adolescent clinical sample, the current study highlights that FH density of alcohol and drug dependence is a risk factor for poorer long-term outcomes for adolescent-onset ASUD youth as they transition into adulthood. Future work should explore the mechanisms underlying greater post-treatment substance use for adolescents/young adults with greater FH density.