Placebo effects in treating migraine and other headaches.

Evaluating the efficacy of a drug therapy in the acute and prophylactic treatment of migraine requires the conduct of placebo-controlled, randomized clinical trials. In order to plan and conduct these studies in the most appropriate manner, it is desirable to know which factors influence the placebo response. This editorial overview discusses the factors that influence placebo response in trials for migraine and other headaches; such factors include expectation, blinding, route of drug administration, patient age and gender, and geographic distribution of the trials. The placebo response rates in the treatment of acute headache episodes are higher than in headache prophylaxis, and invasive procedures, such as injections, have a higher placebo response compared with orally administered drugs.