Improvements in Depression and Mental Health After Acceptance and Commitment Therapy are Related to Changes in Defusion and Values-Based Action.

Acceptance and commitment therapy (ACT) has been found to be effective for various mental health disorders but the processes through which it affects change remain unclear. Much process research in the area is on physical rather than mental health, and focuses on the broad concept of psychological flexibility with little research on specific mechanisms identified in theory such as fusion and values. This study explored whether there was a relationship between two of the main ACT processes (cognitive defusion and values) and levels of depression and distress. Thirty-three participants completed questionnaires at the start and end of their treatment measuring general mental health and distress, depression, levels of cognitive fusion and how much they were living in line with their values and how important their values were to them. Results showed reductions in levels of fusion and increases in values-based action were significantly related to reductions in distress and depression. There was no correlation between changes in values importance and changes in distress or depression. This study therefore suggests decreased defusion and increased values-based action is an important mechanism in the efficacy of ACT in those with depression and mental health problems. The study is however limited by a small sample size and future research with a sample large enough for mediation analysis would be beneficial.