Fitness-impairing disorders, including migraines, tend to disappear as a result of natural selection, and their frequency decreases to near the rate of spontaneous mutation.
[1] This could suggest that a central nervous system (CNS) susceptible to severe, intermittent headache has been linked to an important survival or reproductive advantage.
[medical citation needed][5] A number of specific variants of genes increase the risk by a small to moderate amount.
[9] Another genetic disorder associated with migraine is CADASIL syndrome or cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy.
][12] Similarly, the low threshold for nausea and vomiting may be a mechanism to enhance the elimination of ingested toxins in food.
Migraineurs have a lower prevalence of malignant neoplasms in the brain than controls, suggesting that migraines are protective against tumours.
The first possibility is that migraine offers an advantage to the organism in fighting infection by increasing blood flow to the brain.
Modern environmental factors, with an increased sensory overload, may be especially permissive of the expression of genes that predispose to the disorder.
][16] The compromise between genetic harms and benefits is commonly seen in other disorders, such as cystic fibrosis and sickle cell anemia.
Evidence has suggested a dysfunction of pain-inhibitory pathways in migraine and discordant interaction between the ancient brain stem design and the more evolved neocortex.