Many have proposed that Acceptance and Commitment Therapy (ACT) may be particularly effective for improving outcomes in chronic disease/long-term conditions, and ACT techniques are now being used clinically. However, reviews of ACT in this context are lacking, and the state of evidence is unclear. This systematic review aimed to: collate all ACT interventions with chronic disease/long-term conditions, evaluate their quality, and comment on efficacy. Ovid MEDLINE, EMBASE and Psych Info were searched. Studies with solely mental health or chronic pain populations were excluded. Study quality was then rated, with a proportion re-rated by a second researcher. Eighteen studies were included: eight were randomised controlled trials (RCTs), four used pre-post designs, and six were case studies. A broad range of applications were observed (e.g. improving quality of life and symptom control, reducing distress) across many diseases/conditions (e.g. HIV, cancer, epilepsy).However, study quality was generally low, and many interventions were of low intensity. The small number of RCTs per application and lower study quality emphasise that ACT is not yet a well-established intervention for chronic disease/long-term conditions. However, there was some promising data supporting certain applications: parenting of children with long-term conditions, seizure-control in epilepsy, psychological flexibility, and possibly disease selfmanagement.

training programme. An experienced ACT clinician and trainer, he has an interest in the application of ACT to improving outcomes in chronic disease populations.

Impact and Implications-Psychological interventions offer a potential way to improve outcomes in MDs, which are progressive and mostly without disease modifying treatment. Yet, a dearth of a research using longitudinal designs means that we are unsure which psychological variables represent viable treatment targets in this context.-In line with the theoretical assumptions implicit in Acceptance and Commitment Therapy (ACT), this study suggests that psychological flexibility is a distinct process, which influences life satisfaction and anxiety in muscle disorders. Results: A sample of 137 people with a range of muscle disorders participated. In crosssectional analyses, psychological flexibility explained significant unique variance in addition to illness perceptions ( R 2 = 0.17-0.34, p = <.001). In prospective analyses, psychological flexibility alone was predictive of change in life satisfaction ( R 2 = 0.04, p = .01) and anxiety ( R 2 = 0.03 p = .04) over four months. No independent variables were predictive of change in depression over four months, and disability level had no significant influence on outcomes.Conclusions: Psychological flexibility influences important outcomes in muscle disorders.Experimental studies are required to establish if increased psychological flexibility leads to improved outcomes.