The effectiveness and cost-effectiveness of Acceptance and Commitment Therapy as a transdiagnostic intervention for...

Although the prevalence of psychological problems in transitional-age youth (i.e., youth aged 15 to 25; TAY) is high, TAY are much less likely to receive age-appropriate treatments for their psychological problems compared to younger adolescents or older adults. Hence, effective interventions for TAY seem warranted. ACT your way is a transdiagnostic treatment, specifically developed for TAY, based on the principles of Acceptance and Commitment Therapy (ACT). ACT your way is not directed primarily at symptom reduction, but mainly aims to change the underlying mechanism of psychopathology, namely increasing TAY's psychological flexibility. Meta-analyses show that ACT is an effective treatment for adults with diverse types of psychopathology. Less is known about the effectiveness of ACT for TAY. Therefore, the goal of this study is to examine the effectiveness and cost-effectiveness of ACT your way. In addition, we will investigate for whom and under what circumstances (i.e., moderators) and how (i.e., mediators) the intervention is (most) effective.

The study is designed as a multi-centre, randomized controlled trial. In total, 140 TAY diagnosed with any psychological disorder will be randomly assigned to either the ACT your way or treatment as usual (TAU) condition. In total, six assessments will be conducted: at baseline, after 3, 6 and 9 sessions, at post-intervention and at 6-month follow-up, using multiple informants (TAY, parents/caregivers, therapists). Assessments will include diagnostic interviews and questionnaires. The primary outcomes are psychological flexibility and number of DSM-5 diagnoses; the secondary outcomes are the presence of the primary DSM-5 diagnosis, psychopathology, personality problems, global, individual and societal functioning, quality of life, stress, treatment satisfaction, treatment drop-out and therapeutic alliance. We will also assess costs and various moderators (i.e., demographic characteristics, type and severity of problems, psychopathology of parents/caregivers, treatment expectancy and previous treatments) and mediators (i.e., psychological flexibility, emotion regulation, self-compassion, autonomy, perfectionism, self-esteem and group cohesion).

To our knowledge, this is the first study investigating the (cost-)effectiveness of ACT compared to TAU in clinically referred TAY with various types of psychopathology, using a rigorous design.

The research project is registered in the Dutch Trial Register (Trial NL9642).