The mystery of migraines

Why do people get migraines? It’s a simple question, but one with an incredibly complicated answer. If ‘answer’ is even the right word. Because, in truth, as far as the science is concerned, the most honest and straightforward answer to ‘why do people get migraines?’ would be ‘we don’t know’. Despite countless years of research and study, it seems that the underlying science of migraines is so nuanced and complex that our understanding is still far from complete.

However, it’s always worth emphasising that ‘incomplete understanding’ is a far cry from ‘zero understanding’. Science has revealed many significant things about migraines, why they occur, why they endure, who they affect, and why they hit us so severely.

For those lucky enough to not have to deal with them, it’s easy to label migraines as a type of headache. However, while ‘headache’ is an undeniable aspect of the experience of a migraine, migraines are actually much more than just a headache, and have numerous key differences.

For one, headaches are more common than migraines. Estimates suggest that 75 per cent of all people will have experienced at least one headache within the last year. By contrast, evidence suggests that just under 15 per cent of people experience migraines, with less than 10 per cent of those having chronic migraines.

There’s also a much clearer gender divide with migraines, with between two to three times as many women enduring them as men (a ratio that fluctuates depending on stage of life).

Also, while there is uncertainty and overlap, headaches and migraines have distinct features. The more common types of headache are tension headaches (the feeling of pressure or tension on both sides of the head), sinus headaches (the result of congestion, where the sinus passages swell and put pressure on tissues behind and around the eyes and nose, causing pain), and cluster headaches (painful, repeating headaches, often localised to around the eye regions on one side of the head).

While these headaches can be misdiagnosed as migraines, and vice versa, migraines typically have their own unique features that set them apart. They tend to be much more debilitating, with increased fatigue and sensitivity to light. They also last longer (and have a bizarrely reliable form of progression, with distinct stages), and include nausea and, in many cases, sensory distortions, like the perception of ‘auras’.

Ultimately, while there is undeniably a lot of overlap, migraines have a different mechanism and expression compared to most headaches, to the extent that they’re officially recognised as a neurological disorder, where headaches usually aren’t.

The fact that we’re still unsure about how and why migraines happen seems even more surprising when you consider how long we have been dealing with them. Texts from Ancient Egyptians and Greeks, dating as far back as 1200 BC, describe specific ailments and experiences that are indicative of migraines.

Among the many complicated processes we now know are taking place in the head and brain when a migraine occurs, if there’s one that’s likely to be at the root of them all, it’s what’s known as cortical spreading depression, or CSD.

Science Focus