What happens in your brain during a migraine

A migraine is not just a bad headache—it is a neurological event, meaning something changes in how your brain and nervous system work. During a migraine, blood vessels in your brain constrict (tighten) and then dilate (widen), and chemicals called neurotransmitters flood the area. This combination causes the throbbing pain, and often the nausea, light sensitivity, and other symptoms that come with it.

Researchers believe the process starts in the brainstem, the part of your brain that controls basic functions like sleep and pain. A wave of electrical activity spreads across the brain's surface, followed by inflammation in the blood vessels and protective tissues around the brain. This is why migraine pain often feels like it is centered behind one eye or on one side of the head—the inflammation is happening in a specific region, not all over.

The exact trigger that sets this off varies from person to person. Your brain may be more sensitive to certain signals because of how your genes are wired, how your hormones fluctuate, or how your environment affects you on a given day.

Key Takeaways

  • Migraines involve changes in blood vessel size and the release of chemicals in the brain, not just muscle tension or stress.
  • Genetic factors make some people's brains more prone to migraine, which is why migraines often run in families.
  • Hormonal shifts, especially in people who menstruate, can trigger or worsen migraines.
  • Common migraine triggers include certain foods, sleep changes, stress, and sensory stimuli like bright light or strong smells.
  • Identifying your personal triggers is one of the most useful steps in managing migraines.

How genetics influence migraine risk

If your parents or siblings have migraines, you are more likely to have them too. Researchers have found that certain genetic variations make the brain more reactive to triggers. These genes affect how your brain handles serotonin (a chemical that regulates mood and pain) and how your blood vessels respond to stress or hormonal changes.

Having the genetic predisposition does not mean you will definitely have migraines—it means your brain is wired in a way that makes migraines possible. Whether you actually experience them depends on whether you encounter your personal triggers and how often. Two siblings with the same genes might have very different migraine patterns because their lives and exposures are different.

Hormonal changes and migraine

For people who menstruate, hormonal fluctuations are one of the strongest migraine triggers. Migraines often worsen or begin around puberty, when hormones shift dramatically. Many people notice their migraines follow their menstrual cycle—often occurring just before, during, or just after their period, when estrogen levels drop.

Pregnancy can change migraine patterns unpredictably. Some people find their migraines improve during pregnancy, while others experience them more frequently or severely. Hormonal birth control and hormone replacement therapy can also affect migraine frequency and intensity, though the effect is different for each person.

Menopause brings another hormonal transition that can shift migraine patterns again. These hormonal connections are why keeping a migraine diary—noting when migraines occur in relation to your cycle—can help you and your doctor spot patterns and plan treatment.

Common migraine triggers

A trigger is something that sets off the migraine process in your brain. Common triggers include skipped meals, dehydration, sudden changes in sleep schedule, and caffeine withdrawal. Stress itself does not always trigger a migraine, but the release of stress—like the relaxation after a tense work week—often does.

Sensory triggers are powerful for many people. Bright or flickering lights, loud noises, and strong smells (perfume, cleaning products, smoke) can all provoke a migraine. Some people find that certain foods trigger migraines, though the list varies widely. Commonly reported food triggers include aged cheeses, cured meats, chocolate, and foods containing monosodium glutamate (MSG). Alcohol, especially red wine and beer, triggers migraines in some people.

Weather changes—drops in barometric pressure, high humidity, or temperature shifts—trigger migraines in many people, though scientists are still working out exactly why. Physical exertion, especially sudden intense exercise, can also bring on a migraine, particularly if you are not used to that level of activity.

Why some people's brains are more sensitive

People with migraines have brains that are more reactive to stimulation. Brain imaging studies show that people prone to migraines have different patterns of electrical activity and blood flow compared to people without migraines. Their nervous systems seem to amplify signals that others' brains filter out or ignore.

This heightened sensitivity may be protective in some ways—people with migraines often have keen sensory perception and may notice details others miss. But it also means their brains require more stable conditions to function comfortably. Disruptions that would barely register for someone else—a slight change in routine, a new smell, a missed meal—can tip the balance and trigger a migraine.

This is why migraine management often focuses on stability: keeping a regular sleep schedule, eating at consistent times, staying hydrated, and managing stress. These are not just general wellness advice—they are ways to keep your brain's environment as steady as possible.

The role of serotonin and other brain chemicals

Serotonin is a neurotransmitter—a chemical messenger in the brain—that plays a major role in migraine. During a migraine, serotonin levels fluctuate abnormally. Early in a migraine, serotonin levels spike, causing blood vessels to constrict. Later, serotonin levels drop, and blood vessels dilate, which contributes to the pain.

Other neurotransmitters are involved too. Dopamine, glutamate, and neuropeptides all shift during a migraine. These chemical changes are why certain medications work: some migraine drugs (called triptans) mimic serotonin and help restore balance, while others work by blocking inflammatory chemicals or stabilizing nerve activity.

Understanding these chemical processes has helped doctors develop treatments that target the underlying migraine mechanism rather than just masking the pain. This is also why taking a migraine medication early—as soon as you recognize a migraine is starting—often works better than waiting until the pain is severe.

Environmental and lifestyle factors

Your daily habits and surroundings shape how often migraines occur. Irregular sleep is one of the most common triggers—both too little sleep and oversleeping can provoke a migraine. Skipping meals or going too long without eating drops your blood sugar, which can trigger an attack. Dehydration is another frequent culprit, especially if you are also consuming caffeine, which is a diuretic.

Caffeine itself is complicated: regular caffeine use can prevent migraines for some people, but sudden changes in caffeine intake—either increasing it or cutting back—often trigger migraines. This is why people trying to reduce caffeine should do it gradually rather than quitting cold turkey.

Stress and emotional tension affect migraine risk, though not always in obvious ways. Chronic low-level stress may not trigger a migraine, but acute stress or the letdown after stress often does. This is why migraines sometimes hit on vacation or the weekend, when you finally relax after a stressful period.

Frequently Asked Questions

Can migraines be caused by something serious like a brain tumor?

Migraines themselves are not caused by tumors or other serious brain conditions. However, if your migraine pattern changes suddenly—if they become much more frequent, more severe, or different in character—or if you develop new symptoms, you should see a doctor to rule out other causes. A doctor can determine whether your symptoms fit the migraine pattern you have had or whether something else needs investigation.

Why do migraines run in families?

Migraines run in families because of shared genes that make the brain more reactive to triggers. If both your parents have migraines, your risk is higher than if neither does. However, genetics is not destiny—having the genes means you are more likely to have migraines, but environmental factors and triggers still play a major role in whether and how often they occur.

Can stress alone cause a migraine?

Stress can trigger migraines, but the timing is often counterintuitive. The stress itself may not cause the migraine; instead, the migraine often comes during the relaxation period after stress ends. This is sometimes called a "letdown migraine." This is why migraines frequently occur on weekends or vacations, even though those are supposed to be relaxing times.

Do all migraines have the same cause?

No. While all migraines involve similar changes in the brain—blood vessel dilation, neurotransmitter shifts, and inflammation—the triggers that set off those changes vary from person to person. One person's migraines might be primarily hormonal, while another's are triggered by food or light. This is why identifying your own triggers is more useful than following a generic list.

Can weather really cause migraines?

Many people report that weather changes trigger migraines, particularly drops in barometric pressure. Research supports this connection, though scientists are still working out the exact mechanism. It may involve changes in air pressure affecting the sinuses or brain, or it may be related to how weather affects sleep, activity level, or mood. If you notice a pattern between weather and your migraines, tracking it can help you prepare.