This book discusses the role of placebos and nocebos in the treatment of headache disorders. These disorders are usually treatable, but safety and tolerability issues mean that available preventive treatments have often limited success, even in the right hands   one in five patients treated with a migraine preventive pharmaceutical agent discontinues treatment for those reasons. The nocebo effect plays a role here, with patients  negative expectation and previous unpleasant treatment experiences creating negative belief in the treatment s benefits and safety, which in turn limits treatment outcomes and adherence significantly. In RCTs on migraine prevention, one in 20 patients treated with a placebo discontinued treatment because of adverse events, indicating a considerable nocebo effect; the fewer potential adverse events described in the consent form, the smaller the nocebo effect.