The placebo response in studies of acute migraine

Abstract

Objectives: To characterize the magnitude of the placebo response in trials of migraine therapy in children and adolescents, and to identify its determinants.

Study design: MEDLINE and CENTRAL were searched through November 2006 for randomized controlled trials or controlled clinical trials of pediatric acute migraine pharmacologic treatment that included a placebo comparator group. The main outcomes were headache relief and pain-free response, and effect estimates for risk differences were calculated whenever possible. The influence of placebo response determinants was studied using subgroup analysis. A total of 13 trials (1324 participants in the placebo groups) were included in the analysis.

Results: The pooled placebo responses for pain relief and pain-free at 2 hours were 46% (range, 38% to 53%) and 21% (range, 17% to 26%). Parallel studies conducted in North American centers demonstrated a significantly higher placebo response, as did trials that used 4-point pain scales. Other placebo determinants did not influence the effect estimate, although insufficient data were available to study some of them.

Conclusions: There is a widely variable placebo response in pediatric migraine trials, supporting the continued use of placebo groups and suggesting the need for more research into the placebo effect in the pediatric population.