The basic mechanism: blood vessels and nerve signals

A migraine happens when blood vessels in your brain constrict (tighten) and then dilate (widen), and at the same time, nerve fibers around those vessels release chemicals that cause inflammation and pain. The exact sequence and which part happens first is still debated among researchers, but the result is the same: intense, throbbing pain, often on one side of the head.

This is not the same as a tension headache, where muscles tighten. In a migraine, the problem originates in how your nervous system is wired to respond to certain triggers. Your brain's pain-sensing nerves become hyperactive, and the protective membranes around your brain swell. The chemical serotonin, which helps regulate pain signals, drops during a migraine, which makes the pain worse.

Key Takeaways

  • Migraines involve blood vessel changes and the release of inflammatory chemicals around nerves in the brain, not just muscle tension.
  • Serotonin levels drop during a migraine, which is why some migraine medications work by raising serotonin back up.
  • Common triggers include hormonal changes, certain foods, sleep disruption, stress, and sensory overload, but triggers vary widely between people.
  • Genetics play a major role—if both parents have migraines, you have a higher chance of having them too.
  • Migraines can be managed through identifying your personal triggers, preventive medications, and acute treatments taken at the first sign of pain.

Why genetics matter more than most people realize

If one parent has migraines, your risk is roughly 50 percent. If both parents have them, the risk rises to around 75 percent. This is not because migraines are inherited as a single gene—they are not. Instead, you inherit a tendency for your nervous system to be more sensitive to triggers and to overreact when those triggers appear.

Researchers have identified several genes that affect how your brain handles pain signals and how blood vessels respond to stress. People with these genetic variations have brains that are more excitable overall. This does not mean you will definitely get migraines if your parent did, but it means your nervous system starts from a different baseline than someone without the family history.

Hormonal changes and why women have migraines more often

Women are two to three times more likely to have migraines than men, and hormones are a major reason. Fluctuations in estrogen—particularly the drop that happens right before menstruation—trigger migraines in many women. Some women notice their migraines worsen or improve during pregnancy, and others find that hormonal birth control or hormone replacement therapy changes their migraine pattern.

The connection is not fully understood, but estrogen affects serotonin receptors and blood vessel function, both central to how migraines develop. Tracking when your migraines occur relative to your menstrual cycle can help you and your doctor spot this pattern. If hormonal triggers are clear, your doctor may suggest preventive medication timed to your cycle, or a different form of birth control.

Common triggers and why they vary from person to person

Certain things reliably set off migraines in many people: skipped meals, dehydration, too much or too little sleep, bright lights, loud noises, strong smells, and sudden weather changes. Stress itself does not always trigger a migraine—sometimes it is the release of stress that does, which is why some people get migraines on the first day of vacation.

Food triggers are real but highly individual. Aged cheeses, cured meats, chocolate, caffeine, and alcohol (especially red wine and beer) appear on many trigger lists, but not everyone with migraines reacts to them. The only way to know your triggers is to keep a record: write down what you ate, how much you slept, stress level, and when the migraine started. After a few months, patterns usually emerge.

Caffeine is tricky because it can both trigger and relieve migraines. Regular caffeine use can lower your migraine threshold, but sudden withdrawal causes migraines in people who drink it daily. If you think caffeine is a trigger, cutting back slowly over a week or two is safer than quitting cold turkey.

How your brain's electrical activity changes during a migraine

Researchers have observed a wave of electrical activity that spreads across the brain during a migraine, called cortical spreading depression. This wave of activity is followed by a period of reduced electrical activity. This spreading wave may be what causes the aura—the visual disturbances, tingling, or other sensory symptoms that some people experience 20 to 60 minutes before the headache pain starts.

Not everyone with migraines has an aura, and the aura does not always precede pain. But when it does, it gives you a window of time to take medication before the pain becomes severe. The electrical changes also trigger the release of those inflammatory chemicals around the nerves, which is why the pain can be so intense.

Inflammation and the role of nerve chemicals

During a migraine, nerve fibers release a chemical called calcitonin gene-related peptide (CGRP), which causes blood vessels to dilate and surrounding tissue to swell. This swelling presses on pain-sensing nerves, creating a feedback loop: more inflammation triggers more pain signals, which trigger more inflammation. This is why newer migraine medications target CGRP directly—blocking it can break this cycle.

Other chemicals involved include glutamate (which amplifies pain signals) and substance P (which transmits pain). Understanding these chemical messengers has led to better treatments. Triptans, a common migraine medication, work by narrowing blood vessels and blocking the release of these inflammatory chemicals. Preventive medications work differently—they raise serotonin levels or block CGRP before a migraine starts.

Why stress and sleep disruption are such powerful triggers

Stress and poor sleep both lower your migraine threshold—they make your nervous system more reactive overall. During stress, your body releases hormones like cortisol and adrenaline, which affect blood vessel function and pain perception. Sleep deprivation does something similar: it raises inflammation in the brain and lowers serotonin.

This is why people often get migraines during or right after a stressful period, or after a night of poor sleep. The trigger is not the stress or sleeplessness itself, but the change in your brain chemistry that follows. Managing stress through regular exercise, meditation, or therapy, and protecting your sleep schedule, can reduce how often migraines occur—sometimes dramatically.

Frequently Asked Questions

Can migraines cause permanent brain damage?

Migraines themselves do not cause permanent damage to brain tissue. However, very frequent migraines (more than 15 per month) may be associated with small changes in brain structure over time, though the long-term significance of these changes is not yet clear. Treating migraines early and preventing them when possible is still the best approach.

Why do migraines sometimes run in families but skip a generation?

Migraines are influenced by multiple genes, not just one. You might inherit some of the genes that increase migraine risk but not others, or you might inherit them but not experience the environmental triggers needed to activate them. This is why family patterns can seem unpredictable even though genetics play a real role.

Does caffeine actually help or hurt migraines?

Caffeine can do both. It narrows blood vessels and can relieve pain during an active migraine, which is why it is in some migraine medications. But regular daily use lowers your migraine threshold, and sudden withdrawal triggers migraines. If you drink caffeine daily, keep your intake steady rather than varying it day to day.

Can weather really trigger migraines?

Yes. Changes in barometric pressure, humidity, and temperature affect blood vessel function and can trigger migraines in people who are sensitive. Storms, high heat, and rapid weather shifts are common culprits. Tracking your migraines against weather patterns in your area can help confirm whether this is a trigger for you.

Why do some people get migraines with aura and others without?

The difference lies in whether the cortical spreading depression wave reaches the parts of your brain that handle vision and sensation before it reaches pain-processing areas. Both types involve the same underlying mechanism, but the timing and location of the electrical activity determine whether you experience warning symptoms.