Substance use and co-occurring mental health conditions among adolescents and young adults in North America: a systematic review.

Abstract

BACKGROUND: Substance use and co-occurring mental health conditions are common among adolescents and young adults and represent an important clinical and public health concern in North America. Trauma exposure, psychiatric symptoms, and social adversity frequently co-occur with substance-related problems in this population. This systematic review aimed to synthesize evidence on prevalence patterns, associated clinical and psychosocial factors, and care-related implications described in the literature on adolescents and young adults with substance use and co-occurring mental health conditions. METHODS: This systematic review followed PRISMA guidelines and was preregistered in PROSPERO (CRD42024581685). A systematic search was conducted in MEDLINE (Ovid), Embase, PsycINFO, and Google Scholar. Eligible studies examined adolescents and young adults (≤ 25 years) in North America. A combination of subject headings, keywords, and synonyms for the concepts "adolescents," "young adults," "substance use disorders," and "co-occurring mental health conditions" was used. Of 1,882 records identified, 29 studies met the inclusion criteria. Given the heterogeneity of the literature, findings were synthesized narratively. RESULTS: The included studies showed heterogeneity in population, setting, denominator, and ascertainment method. Across the literature, depressive, anxiety-related, trauma-related, and externalizing mental health presentations were frequently reported alongside substance-related problems in adolescents and young adults. Trauma exposure, adverse childhood experiences, and broader social adversity were also commonly reported in association with substance-related problems across studies. Care-related implications were more limited and were largely derived as future directions mentioned across studies rather than direct evaluations of youth-specific service models. CONCLUSION: Co-occurring mental health and substance-related problems were frequently reported among adolescents and young adults in high-risk and service-engaged populations in North America. Trauma and social adversity were prominent across the reviewed literature, while direct evidence for evaluated, integrated, youth-specific care models remains limited. These findings support the relevance of developmentally appropriate, integrated, and trauma-informed approaches to care and highlight the need for further research directly evaluating improved service delivery models for this population. CLINICAL TRIAL NUMBER: Not applicable.