BACKGROUND: Mental health and substance use disorders typically onset during youth and commonly co-occur. Integrated treatment of two or more co-existing mental health and substance use disorders (i.e., concurrent disorders) is increasingly prevalent in real-world clinical settings. However, the depth of the evidence base on best practices remains unclear.

OBJECTIVES: This scoping review aimed to identify, map and summarize peer-reviewed studies of interventions for concurrent disorders in youth.

METHODS: Six electronic health databases were systematically searched, in addition to a hand search of the reference lists of relevant systematic reviews. Only peer-reviewed studies of interventions treating concurrent disorders (i.e., simultaneous treatment of two or more disorders) in youth (10-29 years old) were eligible. Two independent reviewers conducted screening and data extraction. Results were charted according to studies employing pharmacological and non-pharmacological interventions.

RESULTS: Thirty peer-reviewed studies were included, 19 (63.3%) were randomized controlled trials (RCTs). Most studies enrolled participants with an unspecified substance use disorder (n=17, 56.7%), while alcohol use was the primary substance use disorder in seven (23.3%) studies, followed by cannabis use disorder in six (20.0%) studies. Mood disorders (e.g., depression, dysthymia) were the most common concurrent mental health disorders comprising 15 (50%) studies, followed by nine (30.0%) studies of behavioural disorders (e.g., ADHD) and five (16.7%) studies of unspecified psychiatric disorders. Eighteen (60.0%) studies (n=1,699 participants) investigated the effectiveness of various non-pharmacological interventions, while 12 (40.0%) studies examined pharmacotherapies (n=765 participants).

CONCLUSION: Although several RCTs were identified, substantial clinical and methodological heterogeneity was evident among the studies (e.g., patients with multiple disorders, and multi-faceted interventions). Smaller systematic reviews focused on specific interventions (e.g., behavioural therapies) and concurrent disorders (e.g., depression and substance use) may be warranted. Due to considerable heterogeneity, more RCTs are needed before conducting larger systematic reviews or meta-analyses.