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Endgames Statistical Question

Meta-analyses VI

BMJ 2011; 342 doi: (Published 16 February 2011) Cite this as: BMJ 2011;342:d937
  1. Philip Sedgwick, senior lecturer in medical statistics
  1. 1Section of Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
  1. p.sedgwick{at}

Researchers undertook a meta-analysis of the efficacy of tricyclic antidepressants in the treatment of migraine and tension-type headaches.1 Randomised placebo controlled trials were included if the active treatment group received a tricyclic antidepressant regularly at any dose as a single intervention for at least four weeks.

The primary outcome was burden of headache, typically measured by recording the frequency and intensity of headaches; larger values were indicative of greater burden. For each trial, the standardised mean difference in headache burden was derived because trials did not use the same method of measurement. The standardised mean difference was calculated as the burden in the active treatment group minus that in the placebo group. For each subgroup—tension-type headaches and migraine headaches—a subtotal estimate was derived, then an overall effect estimate was obtained for both subgroups combined.

The results of the meta-analysis were presented in a forest plot.

Forest plot of the effectiveness of tricyclic antidepressants (amitriptyline, clomipramine, amitriptylinoxide, opipramol, or doxepin) compared with placebo in reducing the burden of …

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