ACTing for depressive symptoms : a longitudinal study of a brief 4-session acceptance- and value-based intervention for symptoms of depression

Abstract

The main objective of this study was to investigate a brief 4-session intervention based on a theoretical framework of acceptance and commitment therapy (ACT), and to explore its short- and long-term effectiveness among individuals reporting depressive symptoms. Additionally, the research aimed at further exploring the elements of psychological flexibility and mindfulness associated with improvements in depressive symptoms. The dissertation comprises three studies. Study I investigated the effectiveness of the brief intervention compared to a waiting-list control group. In total, 57 participants were randomized into either the ACT intervention (n = 28) or the waiting-list control (WLC; n = 29) group, the WLC participants receiving the same intervention later. Additionally, both groups were combined at the 6-month follow-up assessment to gather evidence on the short-term outcomes of the intervention. Study II further explored the effects of the brief intervention by extending the follow-up period to five years. Of the original sample, 60% (n = 35) attended the 5-year follow-up measurement. Study III examined the associations of depressive symptoms with psychological flexibility and mindfulness skills with a sub-group of 33 participants. In Studies I and II, reductions in depressive symptoms were detected after the intervention and the outcomes were maintained across the 5-year follow-up period. Significant improvements were also found in other measures and in psychological flexibility during the treatment period with similarly maintained long-term outcomes. The cross- sectional results from Study III showed that higher levels of depressive symptoms at baseline were associated with higher levels of observing and lower levels of psychological flexibility, accepting without judgment and acting with awareness. The findings on treatment-related and long-term changes in depressive symptoms suggest that non-judgmental acceptance was an important factor in the brief intervention. In sum, this study supports the use of the brief 4-hour ACT-based intervention for low mood and emphasizes the importance of developing non-judgmental when treating symptoms of depression.