Although many sufferers have a family history of migraine, the exact hereditary nature of this condition is still unknown. People who get migraines are thought to have an inherited abnormality in the regulation of blood vessels.

"It's like a cocked gun with a hair trigger," explains one specialist. "A person is born with a potential for migraine and the headache is triggered by things that are really not so terrible."

These triggers include stress and other normal emotions, as well as biological and environmental conditions. Fatigue, glaring or flickering lights, the weather and certain foods can set off migraine. It may seem hard to believe that eating such seemingly harmless foods as yogurt, nuts, and lima beans can result in a painful migraine headache. However, some scientists believe that these foods and several others contain chemical substances, such as tyramine, which constrict arteries--the first step of the migraine process. Other scientists believe that foods cause headaches by setting off an allergic reaction in susceptible people.

While a food-triggered migraine usually occurs soon after eating, other triggers may not cause immediate pain. Scientists report that people can develop migraine not only during a period of stress but also afterwards when their vascular systems are still reacting. For example, migraines that wake people up in the middle of the night are believed to result from a delayed reaction to stress.