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Nocebo is the enemy, not placebo. A meta-analysis of reported side effects after placebo treatment in headaches

2011; SAGE Publishing; Volume: 31; Issue: 5 Linguagem: Inglês

10.1177/0333102410391485

1468-2982

Dimos D. Mitsikostas, Leonidas Mantonakis, Nikolaos Chalarakis,

Pain Mechanisms and Treatments

The aim was to determine the magnitude of the nocebo (adverse effects following placebo administration) in clinical trials for primary headache disorders. We reviewed randomized, placebo-controlled studies for migraine, tension-type headache (TTH), and cluster headache treatments published between 1998 and 2009. The frequency of nocebo was estimated by the percentage of placebo-treated patients reporting at least one adverse side effect. The dropout frequency was estimated by the percentage of placebo-treated patients who discontinued the treatment due to intolerance. In studies of symptomatic treatment for migraine, the nocebo and dropout frequencies were 18.45% and 0.33%, but rose to 42.78% and 4.75% in preventative treatment studies. In trials for prevention of TTH, nocebo and dropout frequencies were 23.99% and 5.44%. For symptomatic treatment of cluster headache, the nocebo frequency was 18.67%. Nocebo is prevalent in clinical trials for primary headaches, particularly in preventive treatment studies. Dropouts due to nocebo effect may confound the interpretation of many clinical trials.