Mediators of response to behavioural treatments in CFS
Chronic fatigue syndrome is a chronic illness that can be associated with extreme disability. Patients and clinicians need more information about the effectiveness, safety, and mechanisms of action of currently available treatments. We therefore conducted a large randomised controlled trial (www.pacetrial.org), and found that adding cognitive behaviour therapy (CBT) and graded exercise therapy (GET ) to specialist medical care (SMC) both had greater success in reducing fatigue and physical disability than adding adaptive pacing therapy (APT) to specialist medical care (SMC) or SMC alone . Multiple measures of possible adverse outcomes also indicated that these treatments were safe [1,2]. Improvements occurred irrespective of how the illness was defined .
Our recently published paper was concerned with how CBT and GET worked in the context of the trial . Better understanding of the mechanisms of action is important if we are to improve and individualise treatments and will help to develop new ones. We found that fear avoidance beliefs mediated both CBT and GET. This does not mean that these beliefs cause the illness.
We would like to clarify that we did not say that fear avoidance was the cause of CFS [3,4]. We did not state that the illness was psychological or an exercise phobia. Nor did we say that fear of exercise in CFS was “irrational”. Rather, in an illness where exercise increases symptoms, we believe that being cautious about engaging in activity is understandable . The same processes are important in other chronic illnesses such as low back pain where fear avoidance beliefs have been shown to both moderate and mediate the effects of treatment . Whilst some correspondents have complained that the primary outcomes of the trial were self-rated, we argue that these are the most appropriate measures to judge improvement in an illness that is currently defined by symptoms. We hope that this paper contributes to developing better ways of managing this illness.
1. White PD, Goldsmith KA, Johnson AL, Potts L, Walwyn R, DeCesare JC, Baber HL, Burgess M, Clark LV, Cox DL, Bavinton J, Angus BJ, Murphy G, Murphy M, O’Dowd H, Wilks D, McCrone P, Chalder T*, M Sharpe*, on behalf of the PACE trial management group. Comparison of adaptive pacing therapy, cognitive behaviour therapy, graded exercise therapy, and specialist medical care for chronic fatigue syndrome (PACE): a randomised trial. The Lancet 2011; 377: 823-36.
2. Dougall D, Johnson AL, Goldsmith K, Sharpe M, Angus B, Chalder T, White PD. Adverse events and deterioration reported by participants in the PACE trial of therapies for chronic fatigue syndrome. Journal of Psychosomatic Research 2014; 77: 20-26.
3. Chalder, T., Goldsmith, K. A., White, P. D., Sharpe, M., & Pickles, A. Rehabilitative therapies for chronic fatigue syndrome: a secondary mediation analysis of the PACE trial. Lancet Psychiatry 2015; 2: 141-152.
5. Wertli MM, Rasmussen-Barr E, Held U, Weiser S, Bachmann, LM, Brunner F. Fear-avoidance beliefs—a moderator of treatment efficacy in patients with low back pain: a systematic review. The Spine Journal 2014; 14: 2658-78.
Competing interests: PDW has done voluntary and paid consultancy work for the UK government and a reinsurance company. TC has received royalties from Sheldon Press and Constable and Robinson. MS has done voluntary and paid consultancy work for the UK government, consultancy work for an insurance company and has received royalties from Oxford University Press. KAG and ARP declare no competing interests.