Migraines develop when a network of nerves deep in your brain becomes activated and releases inflammatory chemicals that sensitize blood vessels and surrounding tissue. But the reason that activation happens in the first place varies widely from person to person, involving a mix of genetic wiring, hormonal shifts, environmental conditions, and everyday habits. Understanding both the biology and the triggers can help you recognize patterns and reduce how often attacks occur.
What Happens Inside Your Brain During a Migraine
The pain of a migraine traces back to something called the trigeminovascular system, a network where the trigeminal nerve (the largest nerve in your head) sends branches into the membranes surrounding your brain and the blood vessels that supply them. When this system gets activated, those nerve endings release inflammatory signaling molecules that cause blood vessels to dilate and surrounding tissue to swell. Your brain essentially misreads these signals as intense pain, even though there’s no injury.
One key player in this process is a protein called CGRP. When nerve cells release CGRP, it widens blood vessels, ramps up inflammation, and amplifies pain signaling. CGRP levels spike during a migraine attack and stay elevated, which is why the pain can persist for hours or even days. This protein is so central to migraines that an entire class of newer medications works by blocking it.
In people who experience visual disturbances before the headache (auras), a separate event kicks things off first. A slow-moving wave of electrical activity rolls across the surface of the brain, firing neurons intensely and then silencing them. This wave disrupts normal brain function for minutes at a time, producing those characteristic shimmering lights, blind spots, or geometric patterns. As the wave passes, it dumps inflammatory molecules onto the brain’s outer membranes, which then triggers the trigeminal nerve and launches the pain phase.
Triggers That Set Off an Attack
The biological machinery described above sits in a kind of “ready” state in people prone to migraines. A trigger is anything that tips that system past its threshold. Most people have multiple triggers, and it often takes a combination of them on the same day to start an attack.
Hormonal Changes
Drops in estrogen are one of the most common migraine triggers. Steady estrogen levels tend to keep migraines at bay, but a sudden decline, like the one that happens just before a menstrual period, can set off an attack. This is why migraines are roughly two to three times more common in women than in men during reproductive years, and why attacks often cluster around menstruation, the postpartum period, or the transition into menopause.
Food and Drink
Certain chemicals in food interact with blood vessels and brain chemistry in ways that lower the migraine threshold. Some people don’t process tyramine, an amino acid found in aged cheeses, cured meats, and fermented foods, the same way non-migraine sufferers do. Alcohol is a double threat: it lowers serotonin levels in the brain and causes dehydration, both of which can trigger attacks. Nitrates and nitrites in processed meats like bacon, hot dogs, and deli ham are well-established triggers. Sulfites in red wine and certain compounds in citrus fruits can also raise hormone concentrations in the blood enough to provoke an episode. Caffeine is complicated: small amounts can relieve a migraine in progress, but withdrawal from regular caffeine use is itself a potent trigger.
Environmental Factors
Changes in barometric pressure, the kind that come with approaching storms or shifts in altitude, can trigger migraines by creating imbalances in serotonin and other brain chemicals. Bright or flickering lights, strong smells, loud environments, and sudden temperature swings are also common culprits. Even changes in your sleep schedule, whether too much or too little, can push the system past its tipping point.
Stress and Recovery From Stress
Stress itself is a frequent trigger, but so is the “let-down” period after stress passes. This is why many people get migraines on weekends or the first day of a vacation. The shift in stress hormones appears to destabilize the same neural pathways involved in attack initiation.
Why Some People Get Migraines and Others Don’t
Genetics play a large role in determining who is susceptible. In families where one member has migraines, about 30% of their relatives also have them, compared to roughly 17% in families without a migraine history. Researchers have identified susceptibility genes on chromosomes 4, 6, 11, and 14, along with specific genes that affect how sodium and calcium move in and out of nerve cells. These genetic differences don’t guarantee you’ll get migraines, but they set a lower threshold for the triggers described above.
Nutritional status matters too. Low magnesium levels make nerve cells more excitable because magnesium normally blocks a receptor that controls calcium flow into neurons. Without enough magnesium, nerve cells fire more easily and become more sensitive to pain signals. This creates a lower barrier for that wave of electrical activity that precedes many attacks and makes the trigeminal system more reactive overall. People with frequent migraines are often found to have below-normal magnesium levels.
Migraine incidence peaks in adolescence, with the highest rate of first-time diagnosis occurring between ages 10 and 14. The burden of the condition, measured by how often attacks occur and how disabling they are, peaks between ages 30 and 44.
The Four Phases of a Migraine Attack
A migraine isn’t just a headache. It unfolds in stages, and recognizing the early ones can help you intervene sooner.
Prodrome
Hours or even days before the pain starts, you may notice subtle warning signs: mood changes like irritability or unexplained sadness, difficulty concentrating, fatigue, neck stiffness, food cravings, frequent yawning, or unusual sensitivity to light and sound. Frequent urination and digestive changes (constipation or diarrhea) are also common. Many people learn to recognize their prodrome pattern over time, which provides a window for early treatment.
Aura
About one in four migraine sufferers experience aura, which typically builds over five minutes or more and lasts up to an hour, though it can persist longer in roughly 20% of cases. Visual symptoms are most common: shimmering lights, zigzag lines, blind spots, or geometric patterns that appear in both eyes. Some people also experience tingling, numbness, or difficulty finding words.
Headache
The pain phase lasts anywhere from several hours to three days. Pain is often on one side of the head and has a throbbing or pulsing quality, though it can affect both sides. Nausea, sensitivity to light, sound, and smell, anxiety, and difficulty sleeping are all typical during this phase. Physical activity usually makes the pain worse.
Postdrome
After the headache resolves, many people enter a recovery phase sometimes called a “migraine hangover.” Fatigue, body aches, trouble concentrating, dizziness, and lingering light sensitivity can persist for hours. This phase is often overlooked, but it’s a real part of the attack and a reason many people feel drained even after the pain is gone.
What Lowers Your Migraine Threshold
Think of your migraine threshold as a cup that various factors slowly fill. On a good day, no single trigger is enough to overflow it. On a bad day, several small factors stack up: you slept poorly, skipped a meal, had a glass of wine, and a storm front moved in. The combination pushes you past the tipping point.
This “threshold model” explains why the same trigger doesn’t always cause an attack. It also means that reducing even one or two contributing factors can sometimes prevent migraines, even if you can’t eliminate all of them. Keeping a consistent sleep schedule, staying hydrated, eating regular meals, managing stress, and maintaining adequate magnesium intake all raise the threshold, making it harder for any single trigger to start the cascade that ends in pain.