A migraine happens when pain-signaling nerves in your head become activated and release inflammatory chemicals that sensitize blood vessels and tissues around your brain. The result is a throbbing, often one-sided headache lasting anywhere from 4 to 72 hours, usually accompanied by nausea or heightened sensitivity to light and sound. But the reason you’re having one right now likely comes down to a specific trigger, or a combination of triggers, that set off a brain that was already primed to react.
What’s Happening Inside Your Head
Migraine pain originates in a network of nerve fibers that wrap around the blood vessels and membranes covering your brain. When these nerves fire, they release a signaling molecule called CGRP, which dilates arteries, triggers local inflammation, and activates pain receptors in the protective tissue surrounding the brain. CGRP also amplifies signals between nerve cells, which is why the pain can intensify and spread over time. This same molecule contributes to other migraine symptoms too, including light sensitivity and nausea.
From that initial activation, pain signals travel to a relay hub in the brainstem, then up to the thalamus and across multiple areas of the brain’s surface. That’s why a migraine doesn’t just hurt. It changes how your brain processes everything: sounds seem louder, lights feel blinding, smells become intolerable. Your entire sensory system is dialed up.
The Most Likely Triggers
Migraines rarely appear out of nowhere. Most people can point to at least one trigger, though it often takes a combination to push you over the threshold. In surveys of migraine sufferers, nearly 79% identify lack of sleep as their most common trigger. Skipping a meal comes in second at about 49%. For people who menstruate, hormonal shifts trigger attacks in roughly 47% of cases.
Other well-established triggers include:
- Stress (or the aftermath of stress): Both ongoing tension and the relief period after stress can set off an attack. When stress subsides, your body floods with a signaling molecule that activates inflammatory cells in the membrane surrounding your brain. This “let-down” effect is why migraines often hit on weekends or the first day of vacation rather than during the stressful event itself.
- Sleep disruption: Even a one-hour shift in your sleep schedule can nearly double migraine frequency. A UC Davis study found that the single hour lost to daylight saving time increased migraine days from about 8 to over 13 per 100 person-days. Deep sleep dropped by about 10 minutes per night, and during deep sleep your brain clears metabolic waste most efficiently. Losing that window may be the link between poor sleep and migraine onset.
- Alcohol: Reported as a trigger by a smaller but consistent group of sufferers, roughly 8 to 9%.
- Weather changes, bright lights, and strong smells: These are frequently reported environmental triggers, though they vary widely between individuals.
Why Hormones Play Such a Large Role
Estrogen and progesterone influence the brain chemicals involved in pain signaling. Steady estrogen levels tend to keep migraines at bay, but a drop in estrogen makes headaches worse. The most predictable drop happens in the days just before a menstrual period, which is why so many people with migraines notice a pattern tied to their cycle. Pregnancy, perimenopause, and hormonal contraceptives can all shift the pattern in either direction depending on how they affect estrogen stability.
Genetics Load the Gun
More than half of people with migraines have at least one close family member who also gets them. There’s no single “migraine gene.” Instead, researchers have identified variations across dozens of genes that collectively raise your susceptibility. Many of these genes are active in the muscles surrounding blood vessels in the brain or regulate the excitability of nerve cells. If your parents had migraines, your brain is more likely wired with a lower threshold for activation, meaning triggers that wouldn’t bother someone else are enough to set off an attack in you.
The Four Phases of an Attack
A migraine is more than a headache. It unfolds in stages, and recognizing the early ones can help you respond faster.
Prodrome
Hours or even a day before the pain starts, you may notice mood changes, fatigue, neck stiffness, unusual food cravings, frequent urination, or excessive yawning. These warning signs are easy to miss or attribute to other things, but they’re part of the migraine itself.
Aura
About one in four migraine sufferers experiences aura, which typically involves visual disturbances: flashing lights, shimmering zigzag lines, or blind spots. Aura builds gradually over at least 5 minutes and usually resolves within an hour. Not every migraine includes this phase.
Headache
The pain phase brings moderate to severe throbbing, often on one side of the head, along with nausea, light and sound sensitivity, and sometimes anxiety or difficulty sleeping. This phase lasts anywhere from several hours to three days. Physical activity like walking or climbing stairs typically makes it worse.
Postdrome
After the pain fades, many people feel drained for another day or so. Fatigue, body aches, trouble concentrating, and lingering light sensitivity are common. This “migraine hangover” is often overlooked but is a real part of the attack.
How Migraine Differs From Other Headaches
Clinically, a migraine is identified by a specific pattern: attacks lasting 4 to 72 hours with at least two of these four features (one-sided location, pulsating quality, moderate to severe intensity, or worsening with routine physical activity) plus nausea, vomiting, or sensitivity to both light and sound. A tension headache, by contrast, tends to produce a dull, pressing sensation on both sides of the head without the nausea or sensory sensitivity.
If your headaches are new and you’re not sure what you’re dealing with, tracking the duration, location, and accompanying symptoms over several episodes gives you the clearest picture.
Food Triggers May Be Overstated
You’ve probably heard that aged cheese, chocolate, and red wine cause migraines because of compounds like tyramine. The reality is less clear-cut. A systematic review of studies on tyramine and migraine found that while 17 to 50% of migraine sufferers did get headaches after consuming tyramine, the placebo group also reported headaches at rates up to 42%. That overlap makes it difficult to confirm tyramine as a reliable trigger. The biggest dietary risk factor is simpler: skipping meals. The resulting drop in blood sugar appears to be a more consistent trigger than any specific food.
Red Flags That Need Immediate Attention
Most migraines, while miserable, are not dangerous. But certain headache features suggest something other than a migraine is happening. A sudden-onset headache that hits maximum intensity within seconds (sometimes called a thunderclap headache) can point to a vascular emergency like a brain aneurysm and needs evaluation immediately.
Other warning signs include: fever, night sweats, or unexplained weight loss alongside your headaches; new neurological symptoms like weakness on one side of your body, numbness you haven’t had before, or sudden vision changes; a first-ever severe headache after age 50; headaches that are clearly getting worse over weeks or months; or pain that changes dramatically when you shift positions or strain. Any of these warrant prompt medical evaluation to rule out a secondary cause.