Migraines are caused by a combination of genetic vulnerability, brain chemistry, and environmental triggers that activate pain-signaling pathways in the head. About 45% of migraine risk comes from inherited genetic factors, with the rest shaped by hormones, lifestyle, and the environment. Understanding both the deep biological roots and the everyday triggers can help you make sense of why attacks happen and what makes certain people more susceptible.
How the Brain Generates a Migraine
The central event in a migraine is the activation of the trigeminovascular system, a network of nerve fibers from the trigeminal nerve that wraps around blood vessels in the membranes surrounding the brain. When this system fires, the nerve endings release powerful signaling molecules, most importantly one called CGRP (calcitonin gene-related peptide). CGRP dilates blood vessels inside and outside the skull and amplifies pain signaling. Infusing CGRP directly into a person who gets migraines can provoke an attack, which is strong evidence that it plays a direct role in generating the pain.
This process doesn’t start randomly. The hypothalamus, a small structure deep in the brain that regulates sleep, appetite, and hormones, appears to act as a trigger switch. Brain imaging studies show the hypothalamus becoming active before the headache even begins, during the prodrome phase when people notice food cravings, yawning, or mood changes. The front portion of the hypothalamus seems especially important: it sits between incoming triggers (like sleep disruption or stress) and the brain’s pain-control circuits, essentially deciding when to “let through” a migraine attack.
Cortical Spreading Depression and Aura
About one in four people with migraines experience aura, typically a shimmering arc of jagged lines that starts near the center of vision and expands outward over 5 to 20 minutes, sometimes followed by a temporary blind spot. This visual disturbance maps precisely onto a phenomenon called cortical spreading depression: a slow wave of intense nerve cell activation followed by prolonged silence that rolls across the visual cortex at roughly 3.5 millimeters per minute. Functional MRI studies have tracked this wave in real time, showing a moving change in blood oxygenation that matches the visual symptoms point for point across the brain’s map of the visual field.
Cortical spreading depression can also activate the trigeminal pain pathway, which is why aura typically precedes the headache. But migraines without aura likely involve similar trigeminal activation through other routes, which is why the headache itself feels the same whether or not aura occurs.
Genetics and Family History
Twin studies estimate that 45% of the variation in migraine risk is explained by genetics. If one of your parents has migraines, your chances are significantly higher. This genetic contribution doesn’t come from a single gene. Instead, dozens of common genetic variants each nudge the brain’s excitability, pain-processing thresholds, or vascular reactivity by a small amount. Stacked together, they create a lower threshold for triggering the cascade described above.
What you inherit isn’t migraines themselves but a nervous system that’s more reactive to the triggers that set them off. This explains why two people can face the same missed meal or poor night of sleep and only one develops a migraine.
Hormonal Shifts
Estrogen and progesterone directly influence pain-related chemicals in the brain, which is a major reason migraines are roughly three times more common in women than men after puberty. The most clearly established hormonal trigger is the drop in estrogen that happens just before menstruation. This withdrawal lowers the brain’s pain threshold, making an attack more likely in the day or two leading up to a period.
The same principle plays out during other hormonal transitions. Some women find migraines worsen during perimenopause, when estrogen levels fluctuate unpredictably, then improve after menopause when levels stabilize at a low baseline. Pregnancy often brings relief during the second and third trimesters, when estrogen is high and steady. Hormonal contraceptives can go either way, improving migraines for some and worsening them for others, depending on how they change the estrogen cycle.
Sleep Disruption
Poor sleep is one of the most reliable migraine triggers, and the connection runs through the same biology as the migraine itself. Sleep deprivation creates oxidative stress in the brain, which activates receptors on first-order trigeminal neurons. Those receptors kick off the sensitization process that ultimately leads to CGRP release in the membranes around the brain. In other words, losing sleep doesn’t just make you tired; it directly primes the pain pathway that generates migraines.
Both too little sleep and irregular sleep schedules raise risk. Weekend sleep-ins that shift your wake time by several hours, jet lag, and shift work all disrupt the hypothalamus-driven circadian rhythms that help regulate the migraine threshold. This is one reason many people notice attacks striking in the early morning or on the first day of a vacation when their sleep pattern changes.
Food and Dietary Triggers
Dietary triggers are real but often overstated. In prospective studies using daily headache diaries, about 5% of migraine sufferers recorded attacks on days they consumed nitrates (found in processed meats like hot dogs and deli meat). A cohort study in Turkey found that 10.3% of migraine patients identified cheese as a trigger, likely because of tyramine, a compound that forms as protein-rich foods age. Alcohol, particularly red wine, and caffeine withdrawal are other commonly reported food triggers.
The important nuance is that food triggers are inconsistent. A food might provoke an attack only when combined with other factors like poor sleep, dehydration, or hormonal timing. Keeping a headache diary for a few months is more useful than eliminating entire food groups, because it reveals your personal pattern rather than following a generic avoidance list.
Stress, Sensory Overload, and Other Triggers
Stress is the most commonly self-reported migraine trigger, but the relationship is more complex than “stress causes headaches.” Many people find that attacks hit not during the stressful period itself but in the letdown afterward, such as the first day of a weekend or the start of a holiday. This likely involves shifts in stress hormones and their effects on blood vessel tone and pain modulation.
Bright or flickering lights, strong smells, loud noise, and weather changes (especially drops in barometric pressure) are all well-documented triggers. These sensory stimuli may lower the activation threshold for the trigeminal system in a brain that’s already genetically primed for migraine. Skipping meals is another common trigger, probably through a combination of low blood sugar and hypothalamic signaling related to energy balance.
How Repeated Attacks Change the Brain
Over time, frequent migraines can alter the pain-processing system itself through a process called central sensitization. In the early years of having migraines, most people feel pain only during the headache phase. But with repeated attacks, the neurons that relay pain signals become progressively easier to activate. Eventually, many migraine sufferers develop allodynia during attacks, where normally painless sensations like touching the scalp, wearing a ponytail, or resting on a pillow become genuinely painful.
The threshold for entering this sensitized state depends on the balance between incoming pain signals and the brain’s ability to dampen them through descending pain-control pathways. When attacks are frequent and poorly managed, the pain system tips toward sensitization, which is one mechanism behind the progression from episodic to chronic migraine (15 or more headache days per month). This is why neurologists emphasize prevention early: reducing attack frequency helps preserve the brain’s natural pain-braking system.
Putting the Pieces Together
No single cause explains migraines. Instead, they arise from a threshold model. Your genetics, hormonal status, sleep quality, and stress levels set a baseline. On any given day, a combination of triggers can push you past that threshold and activate the trigeminovascular cascade. This is why migraine patterns can seem so unpredictable: the same trigger that causes an attack one week might not cause one the next, because the other variables have shifted.
Identifying your personal threshold factors, the ones you can modify like sleep regularity, meal timing, stress management, and trigger avoidance, gives you the most practical leverage over a condition that is fundamentally rooted in how your nervous system is wired.