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For doctors, most headache patients are a pain because there are dozens of possible causes. With migraine patients, the problem is quite different; while sufferers can pinpoint certain triggers (food, sleep patterns, stress, alcohol), no one's really sure what exactly causes the condition in the first place. The headaches can last hours — sometimes days — and often come with nausea, vomiting, sensitivity to sound and light, and, perhaps most strangely of all, distorted sensory perception, especially vision. Add to that a link with certain other blood conditions and neurological conditions, and it's no surprise that researchers are still perplexed about the headaches — or that patients seem to find treatment so hit-and-miss.

In the last two weeks, three new studies about the links between migraines and other diseases give good examples of what we've learned so far about the condition and about where researchers might find more clues. The three studies — tying migraines to stroke, depression, and even suicide — may not seem like good news to the 28 million Americans who suffer from migraines, of whom about two-thirds are women. But the studies do highlight the very different ideas researchers have today about the mechanisms that underlie the condition.

The most surprising result is that of 1,400 people who took cognitive tests over several years, those who suffered from migraine with aura (that sensory distortion that sometimes precedes a migraine headache) had less memory loss as they aged than people without migraines did. True, the migraine sufferers generally had worse short- and long-term memory to begin with. "But this is not what we would have expected," says Amanda Kalaydjian, a researcher at the National Institute of Mental Health and the lead author on the study, published in the Apr. 24 issue of Neurology. It suggests there could be some biochemical process in the brain that both causes migraines and limits cognitive degeneration. However, it's also possible, Kalaydjian says, that people with migraine might have been forced by their condition to make lifestyle changes that support cognitive function in old age — like drinking less alcohol, eating better, taking non-steroidal anti-inflammatory drugs, or sleeping more.

The second paper, published in Neurology this past week, finds that middle-schoolers who suffer from migraines with aura are more likely than their peers to suffer from depressive disorders or anxiety disorders — and to be at risk of suicide. While the link between the conditions is poorly understood, the paper, which followed 8,000 youths, notes that altered levels of serotonin — a neurotransmitter affecting mood and appetite — have an impact both on migraine headaches and affective disorders. The study doesn't suggest that migraines make kids suicidal. But it does show that kids with migraines are more likely to be suicidal. It's possible, then, that further research would uncover common biochemical causes.

In the third study, researchers at Duke University took data on nearly 17 million pregnant women, and found that those with migraine were about 19 times more likely to have had a stroke by the time they were discharged than those without. Stroke wasn't the only vascular condition in pregnancy to be more common among migraine sufferers. The results, presented last week at the annual meeting of the American Academy of Neurology, showed a link between migraine and everything from heart attack to preeclampsia. There was no association with non-vascular conditions, like pneumonia or post-partum infection. "This lends credibility to the vascular mechanism of migraines," says lead researcher Cheryl Bushnell, an assistant professor in neurology at Duke. It's also generally recognized that the pain of a migraine headache is caused by dilated blood vessels in the brain.

Where does that all that leave us? None of the new studies contradict each other or the previous literature, although the idea that migraines might somehow prevent against cognitive decay is new. "I certainly think this is going to help as far as people coming up with new theories," Kalaydjian says. All three new studies offer researchers something of value, but none, unfortunately, will bring immediate clarity on how to understand — or how to treat — migraines.

So for those studying migraines, there's new food for thought. For those who suffer from migraines, the new research is a reminder that the best way to protect against deadly associated conditions may still be, quite simply, to look out for other risk factors and avoid triggers. Parents of children with migraines need to be on the look out for telltale signs of depression or anxiety, and expecting mothers should be sure to monitor their heart health. They may not have all the answers, but those doctors may have good news for you yet.

• Laura Blue
• Three recent studies offer very different insight into why people get the debilitating headaches