A hammering headache, fuzzy zig-zags floating in front of the eyes, and an unsettling feeling in your stomach – most people know the symptoms of a migraine. However, despite affecting around a third of people in the world at some point, scientists have long been baffled by this niggling condition.

The science of migraines still isn’t crystal clear, but researchers are starting to build a better picture of what can cause them and their physical mechanisms.

For starters, migraines run in families. If one of your parents experiences migraines, there is a 50 percent chance you will too. If both your parents experience migraines, there’s an approximately 75 percent chance. This suggests to scientists that genes are involved, and they have even managed to hunt down at least 38 areas of the genome that could make you susceptible to them.

Migraines tend to affect women more often than men. This has led some researchers to suggest that hormones like estrogen could play a role. Many people also experience migraines when certain environmental factors trigger them. These triggers can include tiredness, stress, bright lights, strong smells, and spending too much time in front of a computer screen. A surprising amount of people even get migraines when eating certain foods. Just recently, there was the story of a guy who fell severely ill with migraine-like symptoms after eating the “world's hottest chili”.

So that's what can trigger them, but what’s going on inside your head when you have a migraine? There’s much dispute about this, but most scientists think the leading suspects are blood vessels in the brain or neurotransmitters.

Some argue that migraines are caused by a rush of blood to certain cranial vessels, tiny arteries that supply the brain with oxygen, making them dilate and increase in size. The swollen blood vessels then provoke the trigeminal nerve – a large nerve on both sides of the head that supplies sensations to the head and face and controls the muscles used in biting and chewing – to start sending erratic pain signals.

On the other hand, one study used an MRA scanner to image the brains of several patients while they were experiencing migraines and found no change in blood flow to key parts of the brain. This has led others to argue that neurons and abnormal nerve activity are more central to the problem than cranial blood vessels. Patients that experience migraines with an aura (a short period of visual disturbance before the pain) have been shown to have a burst of neuronal activity in the brain followed by a period of inactivity.

Unfortunately, our hazy knowledge about the physical mechanisms behind migraines is partially why they are so hard to treat. However, there is hope on the horizon, with more and more possible treatments being explored. Perhaps most surprisingly of all, ketamine has been found to dull some of the pain of migraines.