Psychological Flexibility, Adaptive Emotion Regulation, Self-Compassion, and Autonomy as Mechanisms of Change in Acceptance and Commitment Therapy for Transitional-Age Youth.

Acceptance and Commitment Therapy (ACT) is a promising transdiagnostic intervention for transitional-age youth (15-25 years) with psychological problems. This study aimed to investigate whether psychological flexibility, adaptive emotion regulation, self-compassion, and autonomy are possible transdiagnostic mechanisms through which ACT reduces psychological problems in transitional-age youth. Data were derived from a randomized controlled trial (RCT) comparing ACT with treatment as usual (TAU). A total of 123 transitional-age youth (M = 17.68, 68.3% female) with various psychological problems participated in the study. Univariate latent growth models were used to assess changes over time in all mechanisms and psychological problems and bivariate latent growth models examined the relationships between changes in each mechanism and changes in psychological problems. Also, we examined whether changes in the four mechanisms served as a potential mediating link between ACT and psychological problems. Results indicated that both ACT and TAU were equally effective in increasing psychological flexibility, adaptive emotion regulation, self-compassion, and autonomy, as well as in reducing psychological problems. In both conditions, increases in psychological flexibility and adaptive emotion regulation were significantly associated with decreases in psychological problems. However, increases in self-compassion and autonomy were unrelated to decreases in psychological problems. These findings emphasize the relevance of psychological flexibility and adaptive emotion regulation as important transdiagnostic intervention targets for psychological problems.