Migraines happen because your brain is more reactive than average to certain internal and external changes. About 14% of people worldwide experience them, and the reasons involve a combination of genetics, nerve signaling, hormones, and environmental triggers that lower your threshold for an attack. Understanding what’s happening in your brain and body can help you identify your personal triggers and reduce how often they strike.
What Happens in Your Brain During a Migraine
The trigeminal nerve, the largest nerve in your head, is central to migraine pain. This nerve carries sensation from your face, scalp, and the membranes surrounding your brain. In people with migraine, nerve fibers projecting from the trigeminal system to blood vessels in the brain’s protective lining become activated and sensitized, essentially firing pain signals when they shouldn’t.
Once these nerve fibers activate, they release a signaling molecule called CGRP that causes blood vessels in the brain to dilate and surrounding tissue to become inflamed. This creates a feedback loop: inflammation sensitizes the nerve endings further, which triggers more signaling, which produces more inflammation. That’s why migraine pain tends to build and worsen over hours rather than hitting all at once, and why it throbs in sync with your pulse.
If you experience aura (visual disturbances, tingling, or speech difficulties before the headache), a separate process is responsible. A slow wave of electrical activity rolls across the surface of your brain at roughly 3 to 5 millimeters per minute, briefly exciting neurons and then shutting them down. This wave, called cortical spreading depression, causes the visual sparkles, blind spots, or numbness that about a quarter of migraine sufferers recognize. It also appears to activate the trigeminal nerve pathway, linking the aura directly to the headache that follows.
Genetics Set Your Baseline Risk
More than half of people with migraine have at least one close family member with the condition. Researchers have identified variations in at least 17 genes associated with migraine susceptibility, though no single gene causes it on its own. Instead, you inherit a collection of small genetic differences that together make your brain more excitable and more sensitive to the triggers described below. Migraine doesn’t follow a simple inheritance pattern like eye color. You can develop it without any family history, and having a parent with migraine doesn’t guarantee you’ll get it. But the hereditary component explains why some people can skip meals, sleep poorly, and drink red wine without consequence while you end up in a dark room for two days.
Hormonal Shifts, Especially Estrogen
If your migraines cluster around your period, you’re not imagining the connection. Migraine attacks correlate with declining estrogen levels, particularly after the hormone has been elevated for a sustained period, exactly what happens in the days before menstruation. A systematic review in JAMA found that no specific estrogen threshold triggers an attack. It’s the drop itself that matters, not how low the level goes. Progesterone levels, by contrast, don’t appear to play a role.
This estrogen connection also explains why migraines often worsen during perimenopause (when hormone levels swing unpredictably), improve after menopause (when levels stabilize at a low baseline), and sometimes change dramatically during pregnancy. Women are roughly two to three times more likely than men to experience migraine overall, and hormonal fluctuations are a major reason why.
Common Triggers and Why They Work
Think of your migraine threshold as a cup that various factors fill up. On a good day, one trigger might not be enough to overflow it. On a bad day, several smaller triggers combine to push you over the edge. Here are the most well-documented ones:
Sleep Disruption
Research from the University of Arizona found that disrupted sleep significantly increases the likelihood of a migraine attack, but the reverse isn’t true: migraine pain doesn’t disrupt normal sleep patterns. This means poor sleep is genuinely a trigger, not just a symptom. Both too little sleep and irregular sleep schedules raise your risk, which is why weekend migraines are common. Your brain craves consistency.
Certain Foods and Drinks
Two naturally occurring compounds in food are the best-understood dietary triggers. Tyramine, found in aged cheeses, cured meats, and fermented foods, causes a release of the stress hormone norepinephrine, which can spike blood pressure and trigger headache pain. Histamine, found in red wine, smoked fish, and pickled vegetables, dilates blood vessels in the brain directly. Both compounds are broken down by enzymes in your gut, but some people process them more slowly, allowing levels to build up. This is why the same glass of red wine might trigger a migraine one day but not another: it depends on what else is in your system and how close you already are to your threshold.
Weather Changes
More than a third of people with migraine report that weather changes noticeably affect their symptoms. A 2017 study found a positive association between shifts in atmospheric pressure and migraine pain intensity. Researchers haven’t pinpointed exact pressure thresholds, but rapid drops in barometric pressure (the kind that precede storms) are the most commonly reported trigger. You can’t control the weather, but tracking it alongside your migraine diary can help you prepare.
Stress and Letdown
Stress itself raises your threshold through cortisol and adrenaline, which is why you might power through a demanding week without a migraine. The attack often comes afterward, during the “letdown” period when stress hormones drop. Weekend and vacation migraines follow this pattern. The trigger isn’t the stress itself but the transition out of it.
How Doctors Determine It’s Migraine
There’s no blood test or brain scan that diagnoses migraine. Doctors use standardized criteria based on your symptoms and history. For migraine without aura, you need at least five attacks that last between 4 and 72 hours when untreated, with at least two of these features: pain on one side of the head, a pulsating quality, moderate to severe intensity, or pain that worsens with routine physical activity like walking or climbing stairs. During the attack, you also need either nausea/vomiting or sensitivity to both light and sound.
For migraine with aura, the bar is lower: just two attacks. But the aura symptoms (visual disturbances, sensory changes, speech difficulties) must be fully reversible, typically lasting between 5 and 60 minutes, and at least one symptom should spread gradually over five minutes or more. This gradual spread distinguishes migraine aura from the sudden onset of symptoms in a stroke, which is an important distinction to be aware of.
Why Your Migraines May Be Getting Worse
If your migraines have become more frequent over time, a few patterns are worth examining. Overusing acute pain medications (taking them more than 10 to 15 days per month, depending on the type) can cause rebound headaches that blend into your migraine pattern, creating a cycle that’s hard to break. Chronic stress, worsening sleep habits, increased caffeine intake, or hormonal changes from aging can all gradually lower your threshold.
Weight gain is another factor. Obesity is associated with more frequent and more severe migraines, possibly because fat tissue produces inflammatory signals that keep the trigeminal system in a state of low-level activation. Conversely, regular aerobic exercise has been shown to reduce migraine frequency, likely by stabilizing stress hormones and improving sleep quality.
Keeping a migraine diary that tracks your sleep, meals, stress, menstrual cycle, and weather conditions for two to three months is the single most useful step for identifying which triggers matter most for you. Many people discover that their migraines follow predictable patterns once they have the data to see them.