Third wave interventions for adolescents with mental health disorders: A systematic review with meta-analysis

Third wave interventions have demonstrated efficacy as a treatment option to promote wellbeing in adolescents. Evidence of their effectiveness for chronic mental health disorders remains unclear. The PubMed, PsycINFO, ProQuest, Embase, and CINAHL databases were searched from inception until March 2024 for five established interventions: acceptance and commitment therapy (ACT), compassion focused therapy, dialectical behaviour therapy (DBT), mindfulness-based cognitive therapy, and mindfulness-based stress reduction (MBSR). Risk of bias was assessed (QualSyst tool), and standardized mean group differences (Hedges’ g) with associated p-values, 95% confidence intervals, and prediction intervals calculated. Three randomized controlled trials and 10 single-group designs, all assessing DBT and representing 700 adolescents (most with subthreshold or full syndrome borderline personality disorder), were included. All studies were of sound methodological quality. DBT was associated with large and significant reductions in mental health symptoms (depression, anxiety, emotional regulation, suicidal ideation, self-harm, and BPD symptoms; g range = 0.69 to 1.05) – although individual variability in treatment response was noted. Symptom improvements were maintained at follow-up (g range = 0.70 to 1.71), although based on limited data. Neither DBT intensity nor duration significantly moderated treatment effects. DBT is the most assessed intervention for adolescents with severe emotional or behavioral problems. Additional controlled studies with diverse samples are needed to confirm the unique effects of DBT relative to other promising third wave interventions. Protocol registration: Open Science Framework [https://osf.io/fgd2j/].