Sir, In their reply to Dr Bramsen, De Lange et al. (2008) use a type of circular reasoning: cognitive behavioural therapy (CBT), they say, has previously been shown to be ‘effective’ for chronic fatigue syndrome (CFS) so the change they measured must be due to CBT.

First, it needs to be pointed out that CBT is far from a panacea for CFS. A recent meta-analysis (Malouff et al., 2008) of the efficacy of CBT in treating CFS found an effect size of d = 0.48 (95% CI 0.27–0.69).

In their letter, De Lange et al. (2008) refer to a review by Whiting et al. (2001) as part-evidence for their claim that CBT is effective for CFS. However, this review recommended the use of objective outcome measures e.g.

Outcomes such as ‘improvement,’ in which participants were asked to rate themselves as better or worse than they were before the intervention began, were frequently reported. However, the person may feel better able to cope with daily activities because they have reduced their expectations of what they should achieve, rather than because they have made any recovery as a result of the intervention. A more objective measure of the effect of any intervention would be whether participants have increased their working hours, returned to work or school, or increased their physical activities’.

Given one of the aims of CBT (for CFS) has been said to be ‘increased confidence in exercise and physical activity’ (O’Dowd et al.), we cannot have complete confidence that the improvements recorded in CBT trials thus far represent objective improvements [such as improvements in grey matter volume (GMV)], rather than simply being due to altering how patients answer questionnaires. An INAMI report (2006) on the use of CBT (combined with GET) in over 600 CFS patients in Belgium found that while patients reported improvements on their fatigue scores, there was negligible change on the tests of exercise capacity and there was actually a worsening of their employment status (as measured by the amount of hours worked per week), both at the end of the intervention and at follow-up.

CFS is not generally a progressive condition—improvement often occurs (Nisenbaum et al., 2003; Cairns et al., 2005). Indeed, in a recent uncontrolled study of CBT (Scheeres et al., 2008), co-written by one of the authors (Bleijenberg), a spontaneous recovery rate of 5% was assumed over a similar period as this study. Thus the authors have not proven that the 12% improvement in GMV in CFS was due to CBT. If their logic was applied throughout medicine, control groups would only be required to test if an intervention was effective as measured by one or a limited number of outcome measures. After that, if a positive change in any other outcome measure was recorded in any uncontrolled study, it would be acceptable for pharmaceutical companies and others to claim that this must be due to their ‘effective’ intervention!

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