An Evaluation of Treatment Effects of Acceptance and Commitment Therapy for Outpatient Group Treatment of Adolescents

This study is an evaluation of group-based acceptance and commitment therapy (ACT)—a transdiagnostic therapeutic approach—in adolescents with anxiety and/or depressive psychiatric disorders in a community hospital outpatient setting. The objective was to evaluate treatment effects on 1) symptom reduction and 2) psychological flexibility measured by underlying ACT processes (avoidance, fusion, mindfulness, valued action) and evaluate whether improvements represent reliable and clinically significant change. Measures were completed by 99 outpatients aged 13 to 18 pre- and post-treatment and at 3-month follow-up. Generalized estimating equation analysis and pairwise comparisons were used to identify changes in symptoms and ACT processes over time. Results showed decreases in anxiety symptoms (pre to post d = -.50; post to 3-month follow-up d = -.41); 2) depression symptoms (d = -.51; d = -.46); 3) and avoidance/fusion (d = -.60; d = -.49), increased mindfulness (d = -.70; d = -.34); and enhanced commitment to values-based action from post-treatment to 3-month follow-up (d = .25). About half of participants reporting clinically elevated symptoms before treatment showed reliable and clinically significant improvement 3-months after treatment ended. Results support the utility of group-based ACT with adolescents. This is the first evaluation conducted in Canadian adolescents seeking community hospital outpatient services for wide ranging and complex mental health difficulties. Future research should continue to take a transdiagnostic perspective and include a control or comparison group and adolescents from different settings.