Migraine used to be known as a vascular disorder which is caused by abnormal blood vessels that affected the brain. It was thought that the blood vessels tightened (constricted), reducing blood flow to the brain, which produced the aura. Then the vessels opened (dilated), producing pain.

But The newer theory is that migraine is a neurovascular disorder. The perpetrator may be the brain itself--not the blood vessels, he says. Changes in the brain may cause changes in the blood flow. Also contributing to migraines are brain chemicals called neurotransmitters and channels in nerve cells that regulate the movement of minerals across them.

Migraines have a genetic link. The National Headache Foundation (NHF) estimates that 70 percent to 80 percent of migraine sufferers have a family history of migraine.

While the precise mechanisms of migraine are unclear, experts do know that people with migraines react to a variety of stimuli, called triggers. "The person inherits a predisposition for attacks and in the setting of the appropriate triggers, has an attack," says Lipton.

There's a long list of triggers that can set off an attack, and not everyone has the same triggers. Some triggers, like weather patterns, are uncontrollable, but others, such as diet and behavior, can be modified. "Not keeping the same eating or sleeping patterns can trigger a migraine," says Seymour Diamond, M.D., co-founder and director of the Diamond Headache Clinic in Chicago. "We see them often on weekends when people oversleep and don't have breakfast."

Certain foods or additives may be migraine triggers. Common triggers, according to the ACHE, are hot dogs and luncheon meats containing nitrates, monosodium glutamate (MSG), chocolate, artificial sweeteners such as aspartame, and a chemical called tyramine found in sour cream, yogurt, aged cheeses, and nuts. Alcohol, particularly red wine, is a trigger for many people. Other triggers are physical exertion, fatigue, bright lights, second-hand smoke, some medications and, in women, hormonal irregularities. Anxiety, stress, or relaxation after stress can also be triggers, according to the National Institute of Neurological Disorders and Stroke (NINDS).

Coleman, who has suffered from migraines since he was 6, is concerned about the emphasis some doctors place on stress as a migraine trigger, particularly those who fault the patient for not handling stress well. "It's a myth that the inability to handle stress is the reason people get migraines," he says. "The most stressful thing about migraine is the disease itself and its impact on a person's quality of life."

Burchfield says her migraines are not stress-related, adding that she's pulled all-nighters to do papers or projects, with no migraine. Red wine and MSG are triggers for her. So are weather and altitude changes, making it difficult to travel. "But it's not always predictable," she says. "Not every weather front or glass of red wine will trigger a migraine." A combination of triggers is more likely to set off an attack.