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Bright lights and too much exercise are well-known migraine launchers, but the latest study hints that sufferers may not be as sensitive to these triggers as previously thought. Researchers report in the journal Neurology that commonly suspected migraine triggers might not be responsible for a hurting head after all.

Unlike previous studies of migraine triggers, in which sufferers were asked about what conditions or situations preceded a headache, the scientists exposed 27 migraine patients in a lab to flashing lights, intense exercise or a combination of both to provoke a migraine with aura, a type of headache accompanied by often debilitating visual disturbances. Only a handful of subjects experienced any sort of migraine, and those who did had exercised, suggesting that bright lights may not be to blame. The participants ran or used an exercise bike at maximum effort for an hour, while researchers used a combination of lamps, flashes and other visual stimuli to mimic light disturbances for up to 40 minutes in order to study the combined effect of light and exercise. After these sessions, only 11% of the participants — three patients — experienced migraines with auras, and an additional 11% experienced migraines without auras.

“What have generally been reported as sure triggers for migraines are not so sure when you actually expose people to them” says Dr. Jes Olesen, the study’s corresponding author from the University of Copenhagen in Denmark and a fellow of the American Academy of Neurology.

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Dr. Stephen D. Silberstein, a professor of neurology at Thomas Jefferson University and the director of the Jefferson Headache Center who co-wrote an accompanying editorial for the study, suggests that some of what people think are triggers may actually be symptoms of migraines instead.

“You eat chocolate and you get a headache. Does that mean chocolate triggers the headache?” Silberstein asks. “What probably happens is the first symptom of your migraine attack is the desire to eat chocolate. Just like when you’re pregnant, you might want pickles or ice cream. That’s one end of the spectrum, where the desire to do something is part of the migraine attack, not the trigger.”

Distinguishing between triggers and symptoms is challenging, not just for those who study migraines but for patients as well. Silberstein says there are some known triggers, such as certain odors, hunger, chemicals in alcohol and hormonal changes linked to menstruation, but that other factors may fall somewhere between an actual trigger and a symptom. How can patients tell? “Everybody with a migraine should try to find out what is triggering their attacks,” Olesen says. “When they have a suspicion, it would be a good idea to try and see if it induces an attack. In most cases, it’s probably not going to be true.”

Both Olesen and Silberstein say there are a number of factors that determine whether these suspected triggers will actually lead to an attack. Patients likely have individual thresholds that vary from day to day and from environment to environment: some days your brain is less vulnerable to certain triggers, while on other days the conditions might be right for a migraine.

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Stress, for example, is one of the most commonly reported migraine triggers, and bright lights and exercise may simply be markers for when stress levels are high. The fact that only exercise appeared to trigger migraines came as a surprise to Olesen, considering a majority of the study’s participants believed bright lights induced migraines more than half the time upon exposure. “The patients were almost apologetic to us because they had indicated it would cause an attack, but it didn’t,” Olesen says.

If these suspected triggers aren’t causing migraines, though, why have they been fingered as responsible for the headaches? Most of the evidence linking the triggers to migraines comes from studies in which patients self-reported what they thought were the factors responsible for their headaches; for the most part, these factors weren’t tested in the way that Olesen analyzed the effect of bright lights and exercise on migraines in the lab.

People’s beliefs about migraines may also complicate how researchers explore migraine causes. Similar to the placebo effect, how patients think about migraines will often influence how they experience them. If you’re convinced a certain food will a trigger a migraine, your suspicion might become a reality; if you’re worried you’ll get a migraine, you might just bring about one.

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That’s not to say lights will never cause a migraine. Because the study was conducted in a lab setting, the exposure to triggers may not accurately replicate the conditions that launch a real-life headache. For example, if a migraine strikes after you exit a dark movie theater and walk into bright light, it could be the sudden contrast from the darkness of the theater that made the light problematic. Or, you might have been hungry or sleep-deprived before being exposed to a bright light, which would still make the light a trigger, albeit one of a combination of factors that prime your brain for the headache.

Olesen says researchers have a better understanding of migraines without auras — they have identified certain chemical triggers that have led to the development of a new class of migraine drugs, for example — but migraines with auras continue to be more of a mystery. The findings hint, however, that some long-held truths about avoiding triggers that can induce migraines with aura may be outdated.

“Trigger avoidance is overdone,” Silberstein says. “If you know something is going to cause your headache, whether you believe it as a result of conditioning or reality, avoid it. But people who take away everything in life that they love because it might trigger their headache, that’s useless.” He argues that it’s worth trying to find out what truly triggers your migraines, even if the process is painful. That suffering may be worth it in the long run.

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