Effect of Acceptance and Commitment Therapy on Depression, Chronic Fatigue, and Pain Intensity in Patients with Fibromyalgia Syndrome: A Study with Expectancy Effect

Aims: Patients with Fibromyalgia Syndrome (FMS) have very low psychological flexibility that can lead to severe pain, depression, and other psychiatric disorders. This study aims to evaluate the effect of Acceptance and Commitment Therapy (ACT) on depression, chronic fatigue and pain intensity in patients with FMS. Methods & Materials: This is a quasi-experimental study with a pretest/posttest/follow-up design. A total of 40 patients with FMS referred to Bu Ali Hospital in Tehran, Iran during 2019-2020 were selected using a convenience sampling method and randomly assigned into two groups of intervention (n=20) and wait-list control (n=20). The group ACT was presented at 8 sessions for both groups. Participants completed the Beck Depression Inventory, the McGill Pain Questionnaire, and Krupp’s Fatigue Severity Scale before, immediately after, and three months after the intervention. Repeated measures Analysis of Covariance was used to analyze the collected data. Findings: Treatment based on ACT method had a significant effect on reducing depression, chronic fatigue, and pain intensity in patients with FMS (P=0.001). Conclusion: ACT can reduce depression, pain severity, and chronic fatigue through acceptance of and adaptation to the disease conditions and better interpersonal relationships.