Intended for healthcare professionals

Rapid response to:


Cognitive behaviour therapy for the chronic fatigue syndrome: a randomised controlled trial

BMJ 1996; 312 doi: (Published 06 January 1996) Cite this as: BMJ 1996;312:22

Rapid Response:

Cohen's d value for this study has been calculated to be 0.54

Given that the objective of this study was to "evaluate the
acceptability and efficacy of adding cognitive behaviour therapy to the
medical care of patients presenting with the chronic fatigue syndrome",
some people might be interested in the size of an effect measure, the
cohen's d value, which has been calculated by Malouff et al[1].

For a meta-analysis of the efficacy of CBT for CFS patients, they
calculated, d, using the following method:
"Separate mean effect sizes were calculated for each category of outcome
variable (e.g., fatigue self-rating) and for each type of outcome variable
(mental, physical, and mixed mental and physical). Studies generally
included multiple outcome measures. For all analyses except those that
compared different categories or types of outcome variables, we used the
mean effect size of all the relevant outcome variables of the study. For
analyses comparing different categories or types of outcome variables, we
used the outcome variable as the unit of analysis."

The d value for this study (see Table 1) is 0.54. This would seem to
cast doubt on the authors' claim that "the overall treatment effect was

Tom Kindlon

[1] Malouff, J. M., et al., Efficacy of cognitive behavioral therapy
for chronic fatigue syndrome: A meta-analysis. Clinical Psychology Review
(2007), doi:10.1016/j.cpr.2007.10.004

Competing interests:
Assistant Chairperson, Irish ME/CFS Association - for Information, Support & Research (voluntary position)

Competing interests: No competing interests

10 December 2007
Tom Kindlon
Unavailable for work due to ill-health
Dublin, Rep. of Ireland