Safety and tolerability of both naratriptan and placebo are very well documented. Incidence and nature of side-effects and interactions has been described to be low and relatively mild, also with frequent (daily) use of naratriptan. Patients at risk for side-effects will be excluded from the study. Drugs will be added to the usual medication of the participants. A questionnaire will be administered and blood will be collected upon inclusion in the study. Data including genotype will be processed anonymously.