BACKGROUND AND AIMS: Brief interventions delivered in healthcare settings represent a promising substance use prevention and early intervention strategy for youth in foster care, among whom early life adversity and resulting psychological sequalae increase risk for problematic substance use. Limited research has examined the effectiveness of brief interventions in this subpopulation. This study aimed to examine whether psychological diagnoses were associated with screening positive for problematic substance use, and whether psychological diagnoses impacted effectiveness of a brief intervention for substance use.

DESIGN: Longitudinal observational study of adolescents (ages 10-20 years) seen for mandated health examinations in a foster care clinic. Youth who endorsed substance use and received a brief intervention were invited to complete baseline surveys and follow-ups at 30 days, 60 days and 6 months. Logistic regressions evaluated associations of mental health disorders with endorsing problematic substance use. Generalized linear mixed models examined associations of mental health disorders with trajectories of post-intervention change in substance use.

PARTICIPANTS: Adolescents in Midwest, United States seen for mandated health examinations in a foster care clinic who completed a substance use screening measure [CRAFFT2.1 + N; n = 1656; mean age (SD) = 14.4 (2.6); 53.4% female; 58.4% Black, 31.6% white]. A second subsample included only those adolescents who received a brief intervention for substance use during their clinic visit [n = 287; mean age (SD) = 15.9 (2.1); 59.9% female; 53.7% Black, 35.5% white].

MEASUREMENTS: Mental health diagnoses and CRAFFT2.1 + N were extracted from the electronic health record. Youth-reported count of past 30-day use of alcohol, cannabis and nicotine/tobacco at each wave.

FINDINGS: A minority (12%) of youth in foster care endorsed problematic substance use. Youth with a mental health diagnosis had 58% to 161% higher odds of reporting problematic substance use [odds ratios (ORs) = 1.58-2.61; 95% confidence intervals (CIs) = (1.16-2.13) - (1.93-3.56)]. Following the intervention, youth who had been diagnosed with internalizing disorders (i.e. anxiety, depressive and trauma disorders), and those with co-occurring internalizing and externalizing disorders, reported smaller decreases or no decreases in their cannabis [ORs = 2.09, 7.03; 95% CIs = (1.17-3.71), (3.43-14.42)] and nicotine use [ORs = 1.95-7.68; 95% CIs = (1.08-3.53) - (4.12-14.32)]. Alcohol use did not vary as a function of mental health diagnoses [ORs = 0.31-13.10; 95% CIs = (0.00-19.37) - (0.19-915.80).

CONCLUSION: Foster youth in the United States, particularly those with mental health concerns, appear to be at high risk for problematic substance use.