ORIGINAL ARTICLE Acceptance and commitment therapy for fibromyalgia: A randomized controlled trial R. K. Wicksell 1,2 , M. Kemani 1,2 , K. Jensen 4,5 , E. Kosek 2,6 , D. Kadetoff 2,6 , K. Sorjonen 2 , M. Ingvar 2,6 , G. L. Olsson 1,3 1 Behavior Medicine Pain Treatment Service, Karolinska University Hospital, Stockholm, Sweden 2 Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden 3 Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden 4 Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, USA 5 Athinoula A. Martinos Center for Biomedical Imaging, Boston, USA 6 Osher Center for Integrative Medicine, Karolinska Institutet, Stockholm, Sweden Correspondence Rikard K. Wicksell E-mail: rikard.wicksell@karolinska.se Funding sources One author (E. K.) received support from the Swedish Research Council, Project No. K2009-53X-21070-01-3, the Stockholm County Council, and the Swedish Rheumatism Association. Conflicts of interest The present manuscript is submitted exclusively to European Journal of Pain and is not under consideration in any other journal. There are no financial or other relationships that might lead to a conflict of interest. Accepted for publication 15 August 2012 doi:10.1002/j.1532-2149.2012.00224.x Abstract Background: Fibromyalgia (FM) is characterized by widespread pain and co-morbid symptoms such as fatigue and depression. For FM, medical treatments alone appear insufficient. Recent meta-analyses point to the utility of cognitive behaviour therapy (CBT), but effects are moderate. Within the continuous development of CBT, the empirical support for acceptance and commitment therapy (ACT) has increased rapidly. ACT focuses on improving functioning by increasing the patient’s ability to act in accordance with personal values also in the presence of pain and distress (i.e., psychological flexibility). However, no study has yet explored the utility of ACT in FM. Objectives: To evaluate the efficacy of ACT for FM and the role of psychological inflexibility as a mediator of improvement. Methods: In this randomized controlled trial, ACT was evaluated in com- parison to a waiting list control condition. Forty women diagnosed with FM participated in the study. Assessments were made pre- and post-treatment and at 3 months of follow-up. The ACT intervention consisted of 12 weekly group sessions. Results: Significant differences in favour of ACT were seen in pain-related functioning, FM impact, mental health-related quality of life, self-efficacy, depression, anxiety and psychological inflexibility. Changes in psychological inflexibility during the course of treatment were found to mediate pre- to follow-up improvements in outcome variables. Conclusions: The results correspond with previous studies on ACT for chronic pain and suggest the utility of ACT for FM as well as the role of psychological inflexibility as a mediator of improvement. 1. Introduction Fibromyalgia (FM) is a chronic pain disorder affecting both youths and adults (Buskila et al., 1993), and more women than men (Wolfe F. et al., 1995a). Prevalence rates range between 2.2% and 6.6% in Western coun- tries (Branco et al., 2010). FM is primarily character- ized by widespread pain although fatigue and other somatic or psychological symptoms are commonly reported (Wolfe F. et al., 1995b). Recent neuroimaging studies with FM have demonstrated altered brain func- tions, which support the idea of a dysfunction in top- down pain regulatory mechanisms (Jensen et al., 2009; Lannersten and Kosek, 2010). Although antidepres- 1 Eur J Pain •• (2012) ••–•• © 2012 European Federation of International Association for the Study of Pain Chapters