There are two major theories about the causes of migraine: the neuronal and vascular theories. The neuronal theory - which is more widely accepted today - states that neuronal activity is sufficient to cause a migraine, and is supported by abnormal signal processing and lack of cerebral vasodilation (blood vessel dilation) between episodes, as well as hypothalamic activation during migraines. The vascular theory states that vasodilation is sufficient to cause a migraine, and is supported by the migraine-inducing effects of substances that result in vasodilation and the vasoconstrictive effects of drugs that treat migraines.

Both theories suggest that migraines are associated with the hyperexcitability of local brain tissue due to increased glutamate levels.