Migraines result from a combination of genetics, brain chemistry, and environmental triggers. About 14% of the global population experiences them, and more than half of people with migraines have at least one family member who also gets them. Understanding why migraines happen means looking at two separate layers: the underlying biology that makes certain brains vulnerable, and the specific triggers that set off an individual attack.
The Migraine Brain Works Differently
People who get migraines don’t just have occasional bad headaches. Their brains process sensory information in a fundamentally different way, even between attacks. Research published in Physiological Reviews describes the migraine brain as “dys-excitable,” meaning it over-responds to stimuli that wouldn’t bother someone without migraines.
Between attacks, people with migraines tolerate less brightness than people without them. Their visual cortex activates in response to light levels that produce no such response in non-migraine brains. The same pattern holds for sound and smell. People with migraines who are sensitive to odors show increased blood flow in brain regions involved in scent processing, and their brains fail to “habituate,” or tune out, repeated sensory signals the way other brains do. This habituation deficit is measurable through brain scans and electrical recordings, and it actually normalizes in the days just before an attack, suggesting the brain reaches a tipping point before the migraine fires.
This constant state of sensory over-responsiveness is why bright lights, loud environments, and strong perfumes can feel uncomfortable for migraine sufferers even on their good days, and overwhelming during an attack.
Genetics Set the Stage
Variations in many genes contribute to migraine susceptibility, though no single gene is responsible. Most of the genes identified so far are active in the muscles surrounding blood vessels in the brain, where they help regulate blood flow by controlling how vessels narrow and expand. Other associated genes influence levels of glutamate, a chemical messenger involved in nerve cell signaling, or affect how excitable certain nerve cells are.
Migraines don’t follow a simple inheritance pattern like some genetic conditions. You won’t necessarily get them just because a parent did. But genetics clearly load the dice: more than half of people with migraines have at least one close relative with the condition. What gets inherited isn’t the migraine itself but the brain’s heightened sensitivity to triggers.
What Happens During an Attack
A migraine attack isn’t a single event. It unfolds in phases, sometimes over the course of days.
The earliest phase, called the prodrome, can begin hours or even days before headache pain starts. Symptoms vary but commonly include mood changes (irritability or depression), fatigue, difficulty concentrating, sensitivity to light and sound, nausea, neck stiffness, and muscle tension in the shoulders. Some symptoms are surprisingly specific to this phase: excessive yawning, food cravings, and frequent urination.
About one in four people with migraines also experience aura, which typically involves visual disturbances like shimmering lines, blind spots, or flashing lights. Aura is caused by a wave of abnormal electrical activity that spreads slowly across the brain’s surface, temporarily suppressing normal brainwave patterns. Researchers at the American Headache Society recently captured a direct recording of this phenomenon in a patient. Brainwave activity on one side of the brain went flat and stayed suppressed for hours during the migraine, providing the first direct confirmation of a mechanism scientists had theorized about for decades.
After the headache phase resolves, many people experience a postdrome sometimes called a “migraine hangover.” This can involve fatigue, body aches, dizziness, trouble concentrating, and lingering light sensitivity. The full cycle, from first prodrome symptoms to the end of postdrome, can stretch well beyond the headache itself.
Common Triggers That Start an Attack
Triggers are the environmental and lifestyle factors that push an already-sensitive brain past its threshold. They vary from person to person, and often it takes a combination of triggers rather than a single one to set off an attack.
Stress is the most commonly reported trigger. It activates the nervous system in ways that lower the brain’s threshold for a migraine, and attacks often hit not during the stressful period itself but during the letdown afterward.
Hormonal shifts are a major factor for women. Steady estrogen levels tend to keep migraines in check, but drops in estrogen make attacks more likely. This is why migraines often cluster around menstruation, when estrogen falls sharply. Pregnancy can bring relief for some women because estrogen stays elevated, but migraines frequently return after delivery when estrogen drops suddenly.
Sleep disruption works in both directions. Too little sleep and too much sleep can both trigger attacks. Sleep apnea is also associated with migraines, so people who snore heavily or wake up with morning headaches may want to explore that connection.
Food and drink triggers include fermented or pickled foods, aged cheeses, processed or cured meats (hot dogs, deli meats), and certain preservatives. Alcohol, especially wine, is a well-known trigger. Caffeine has a complicated relationship with migraines: too much can trigger an attack, and so can withdrawal if you’re a regular coffee drinker. Skipping meals or eating at irregular times also increases risk.
Environmental factors include sudden weather changes, shifts in temperature or barometric pressure, bright or flickering lights, loud noise, and strong smells. Seasonal transitions are a particularly common trigger window.
Nicotine from cigarettes and e-cigarettes constricts blood vessels in the brain, which can trigger attacks. And paradoxically, overusing pain medications, including ones meant to treat migraines, can cause rebound headaches that increase migraine frequency over time.
Diet Patterns That May Help
Beyond avoiding individual food triggers, broader dietary patterns appear to influence migraine frequency. NIH research suggests that diets low in vegetable oils and high in fatty acids found in fish may help reduce migraine attacks. This likely relates to inflammation pathways, since the fats in fish oil have anti-inflammatory effects while certain vegetable oils promote inflammation. This isn’t a quick fix, but for people with frequent migraines, shifting the overall balance of fats in the diet is one of the few lifestyle changes with research behind it.
Why Triggers Vary So Much
One of the most frustrating things about migraines is that a trigger that reliably causes an attack one week might be harmless the next. This is because migraine threshold isn’t fixed. It fluctuates based on sleep quality, stress levels, hormonal status, hydration, and how recently you had your last attack. On a day when you’re well rested and relaxed, a glass of wine might be fine. On a day when you slept poorly, skipped lunch, and are under deadline pressure, that same glass of wine could be the final push.
This is why tracking patterns matters more than identifying a single cause. Keeping a record of your sleep, meals, stress levels, and menstrual cycle alongside your attacks can reveal which combinations of factors are most dangerous for you. The goal isn’t to eliminate every possible trigger but to manage the ones you can control so your overall threshold stays high enough to absorb the ones you can’t.