What happens in your brain during a migraine
A migraine is not just a bad headache—it is a neurological event involving changes in blood vessel activity, nerve signaling, and brain chemistry. The exact sequence is still being mapped, but the leading explanation involves a cascade: a wave of electrical activity spreads across the brain's surface, followed by a period of reduced blood flow, then a rebound widening of blood vessels. This vascular shift, combined with the release of inflammatory substances around nerves and blood vessels, produces the throbbing pain.
The trigeminal nerve, which carries sensation from your face and head, plays a central role. When activated during a migraine, it releases neuropeptides—chemical messengers that cause blood vessels to swell and surrounding tissue to become inflamed. This inflammation is what makes the pain worse with movement and light, and why even touching your scalp can hurt.
Importantly, the pain itself is real and measurable, not psychological. Brain imaging during migraines shows genuine changes in blood flow and neural activity. The migraine is not "all in your head" in the sense of being imaginary—it is in your head in the sense that it originates from how your nervous system is functioning.
Key Takeaways
- Migraines involve a wave of electrical activity in the brain followed by changes in blood vessel diameter and the release of inflammatory chemicals around nerves.
- The trigeminal nerve, which senses your face and head, becomes overactive and releases substances that cause swelling and pain.
- Genetic factors make some people's brains more prone to these cascades, which is why migraines run in families.
- Common triggers—stress, hormonal changes, certain foods, sleep disruption, and sensory overload—lower the threshold at which a migraine begins, but do not cause migraines in people without the underlying predisposition.
Why some people's brains are wired for migraines
If migraines run in your family, your risk is significantly higher. Twin studies show that genetics account for roughly 50 to 60 percent of migraine risk, meaning your inherited brain chemistry matters more than your life circumstances. Researchers have identified several genes associated with migraine susceptibility, though no single "migraine gene" exists—instead, multiple genetic variations combine to create vulnerability.
People with migraines appear to have brains that are more excitable and less stable in their electrical activity. Their neurons fire more readily, and their blood vessels respond more dramatically to triggers. This is not a defect or a sign of weakness; it is a difference in how the nervous system is tuned. Some researchers describe it as a lower threshold for the cascade to begin.
This genetic predisposition explains why two people exposed to the same trigger—say, skipping a meal or a stressful day—will have different outcomes. One person gets a migraine; the other does not. The trigger did not cause the migraine; it lowered the threshold enough to tip someone whose brain was already primed.
How hormones influence migraine patterns
Estrogen fluctuations are among the most consistent migraine triggers, particularly for people who menstruate. Many women report migraines clustered around their period, when estrogen levels drop sharply. Some experience migraines only during this window—a pattern called catamenial migraine. Others find their migraines worsen or improve depending on where they are in their cycle.
Hormonal birth control can shift migraine patterns unpredictably. Some people find their migraines decrease on hormonal contraception; others find they increase. Pregnancy often changes migraine frequency—some women see improvement, others see worsening, and some see no change. Menopause typically brings changes as well, though the direction varies widely.
The mechanism involves estrogen's effects on serotonin receptors and blood vessel reactivity. When estrogen levels are stable, migraines may be less frequent. When they fluctuate, the nervous system becomes less stable, and migraines become more likely. This is why tracking your migraine pattern against your cycle can reveal whether hormones are a major factor for you.
Common triggers and how they lower your threshold
A trigger is anything that makes a migraine more likely to occur in someone whose brain is already predisposed. The most frequently reported triggers include stress and stress relief (the "letdown" migraine after a tense period), sleep disruption—both too little and too much—skipped meals, dehydration, caffeine withdrawal, bright or flickering lights, strong smells, and certain foods.
Specific foods implicated in migraine include aged cheeses, cured meats, fermented foods, and those containing monosodium glutamate (MSG). Alcohol, particularly red wine and beer, is a common trigger. Chocolate, citrus fruits, and nuts appear in some people's patterns but not others. The reason these foods trigger migraines in some individuals but not others relates to how their nervous systems process the compounds in those foods—again, it is about predisposition, not the food itself.
Importantly, a trigger does not always produce a migraine. You might skip breakfast on Monday and have no migraine, then skip breakfast on Wednesday and have one. The difference is usually that on Wednesday, you also had poor sleep, stress, or hormonal changes—multiple smaller triggers stacked together. This is why identifying your personal triggers requires tracking patterns over weeks or months, not just noting what happened the day before a migraine.
Why stress and relaxation both trigger migraines
Stress is a well-known migraine trigger, but so is the relief from stress. Many people experience their worst migraines on the first day of vacation or the weekend after a stressful week. This "letdown migraine" happens because stress hormones like cortisol keep the nervous system in a heightened state; when stress drops suddenly, the system rebounds, and that rebound can trigger the migraine cascade.
The mechanism involves changes in serotonin and other neurotransmitters. During stress, certain brain chemicals are depleted or dysregulated. When the stress ends, the system recalibrates, and that shift in chemistry can be enough to cross the threshold. This is why some people find that relaxation techniques, while generally helpful, can paradoxically trigger a migraine if they lower stress too suddenly.
Understanding this pattern can help you manage expectations. If you know you are prone to letdown migraines, you might plan a lighter schedule for the first day of vacation or the weekend, or use preventive strategies during that vulnerable window.
Sensory overload and environmental factors
Bright, flickering, or patterned light is a potent trigger for many people with migraines. Fluorescent lights, screens, sunlight reflecting off water, and strobe effects can all initiate a migraine. The mechanism is not fully understood, but it appears to involve overstimulation of the visual cortex and the trigeminal nerve system. Some people are so sensitive that they wear tinted glasses or adjust their screen brightness to reduce risk.
Strong smells—perfume, cleaning products, smoke—trigger migraines in others. Loud noise or sudden changes in air pressure can also lower the threshold. These sensory triggers do not affect everyone equally; sensitivity varies widely. If you notice a pattern, reducing exposure during high-risk periods (like around your period or during a stressful time) may help prevent migraines from occurring.
Weather changes, particularly drops in barometric pressure, are reported by many migraine sufferers. The biological mechanism is unclear, but the pattern is consistent enough that some people can predict migraines based on weather forecasts. While you cannot control the weather, knowing this is a trigger for you can help you anticipate and prepare.
What research still does not fully explain
Despite decades of research, some aspects of migraine causation remain unclear. Why do some people with the genetic predisposition never have a migraine? Why do triggers vary so much from person to person? Why do migraines sometimes stop for years and then return? These questions suggest that the full picture involves factors we have not yet identified or fully understood.
Ongoing research is examining the role of the gut microbiome, inflammatory markers, mitochondrial function, and other biological systems. New imaging techniques are revealing more detail about what happens in the brain during a migraine. This research may eventually lead to more targeted prevention and treatment, but for now, the understanding is incomplete.
What is clear is that migraines result from an interaction between genetic predisposition and environmental or physiological triggers. Neither alone is sufficient; you need both the underlying brain wiring and something to lower the threshold. This is why two people can have identical triggers but very different migraine patterns.
Frequently Asked Questions
Can stress actually cause a migraine, or does it just make one more likely?
Stress lowers your threshold but does not cause a migraine in someone without the underlying predisposition. In someone whose brain is primed for migraines, stress can be enough to tip the balance. The same stress that triggers a migraine in one person produces no migraine in another.
If migraines run in my family, am I may provide to get them?
No. Genetics account for about half of migraine risk. Having a parent or sibling with migraines increases your likelihood significantly, but environmental factors, lifestyle, and other variables also matter. Some people with a strong family history never develop migraines.
Why do my migraines seem random when I cannot identify a clear trigger?
Migraines often result from multiple small triggers stacking together rather than one obvious cause. Poor sleep plus stress plus skipped breakfast plus hormonal changes might combine to cross your threshold, while any one alone would not. Tracking patterns over weeks helps reveal these combinations.
Does caffeine cause migraines or prevent them?
Both. Caffeine can prevent migraines by narrowing blood vessels and reducing inflammation, which is why it is in some migraine medications. But caffeine withdrawal—suddenly stopping regular use—is a strong trigger. Regular, consistent caffeine use may prevent migraines; sudden changes in intake can trigger them.
Can migraines be caused by something serious like a brain tumor?
Migraines are a primary neurological condition, not a symptom of another disease in the vast majority of cases. However, a new migraine pattern, a significant change in your usual migraine, or migraines accompanied by neurological symptoms like weakness or vision loss warrant evaluation by a doctor to rule out other causes.