Download AppThis is an educational overview rather than medical advice. It describes the current scientific model, which is still an active area of research.
Migraine is classified as a neurological disease, and the biology behind it is better understood than most people assume. Some pieces are still debated, and we will be honest about which ones. But the broad picture has held up well, and it explains a lot about why an attack feels the way it does, and why the newest treatments work the way they do.
A brain that responds differently
At its core, migraine is often described as a disorder of how the brain handles incoming signals. Between attacks, many people with migraine are more sensitive to light, sound, and other input than people without it, and that heightened responsiveness seems to be part of the underlying trait rather than just a symptom of the attack itself. It also tends to run in families, which points to a strong genetic component. In other words, this is something about how a particular brain is built and tuned, not a sign of a fragile personality.
Where aura seems to come from
The leading explanation for migraine aura is something called cortical spreading depression, or CSD. It is a slow wave of changed electrical activity that travels across the surface of the brain at roughly 2 to 5 millimetres per minute, a figure reported consistently in the literature (Cephalalgia review). That pace lines up neatly with how aura symptoms spread and then fade over the course of several minutes. When someone describes a shimmering patch that slowly expands across their vision over twenty minutes, that timing is not a coincidence. It maps onto the wave moving across the visual part of the brain.
How the pain gets switched on
CSD is thought to activate the trigeminovascular system. That is the network of nerves carrying pain signals from the coverings of the brain, the meninges. Once those nerves fire, they release signalling molecules, and the one that gets the most attention is calcitonin gene-related peptide, usually shortened to CGRP. Levels of it rise during attacks, and there is also evidence of altered serotonin signalling (Nature Reviews Disease Primers).
A careful note is worth making here. Whether CSD actually triggers the headache in humans, as opposed to in animal models, is still genuinely debated. The older idea that migraine was mainly a problem of blood vessels dilating has largely given way to this view centred on nerves and brain activity. Older drugs were once thought to work by constricting vessels, but the picture turned out to be more about the nervous system than the plumbing. So when we say CSD is "thought to" set off the pain, we mean it. It is the best current model, not a closed case.
Why CGRP turned out to matter so much
The interest in CGRP is not academic. It is the reason an entire class of modern migraine medications exists. Once researchers understood its role, they could design drugs to block it or block its receptor. In laboratory work, blocking the CGRP receptor even suppressed CSD itself, which tied the molecule back to the cortical events at the very start of an attack (Cephalalgia review). That is a relatively rare and satisfying arc in medicine, where a mechanism worked out in the lab leads fairly directly to treatments that people can actually take, both to stop attacks and to prevent them.
This is common, and it is disabling
None of this describes a rare condition. An estimated 1.16 billion people around the world live with migraine, and it ranks as the second leading cause of disability globally (Global Burden of Migraine, 2024). In the US, roughly 18 percent of women and 6 percent of men are affected (AMPP study summary). Those figures are modelled estimates rather than a literal headcount, so we treat them as approximate, but the scale is not in question.
Understanding the biology does one genuinely useful thing above all. It reframes migraine as what it actually is, a measurable disorder of the brain with real mechanisms and real treatments, rather than a weakness someone ought to be able to push through.