Although both males and females seem to be affected by migraine, the condition is more common in adult women. Both sexes may develop migraine in infancy, but most often the disorder begins between the ages of five and 35.

The relationship between female hormones and migraine is still unclear. Women may have menstrual migraine--headaches around the time of their menstrual period--which may disappear during pregnancy. Other women develop migraine for the first time when they are pregnant. Some are first affected after menopause.

The effect of oral contraceptives on headaches is perplexing. Scientists report that some women with migraine who take birth control pills experience more frequent and severe attacks. However, a small percentage of women have fewer and less severe migraine headaches when they take birth control pills. And normal women who do not suffer from headaches may develop migraines as a side effect when they use oral contraceptives. Investigators around the world are studying hormonal changes in women with migraine in the hope of identifying the specific ways these naturally occurring chemicals cause headaches.