The exact cause of migraines is unknown, although they are thought to be the result of temporary changes in the chemicals and blood vessels in the brain.
Around half of all people who experience migraines also have a close relative with the condition, suggesting that genes may play a role.
Some people find migraine attacks are associated with certain triggers, which can include starting their period, stress, tiredness and certain foods or drinks.
Read more about the causes of migraines.