Women three times likelier to suffer migraine than men, say experts.
An astonishing 25 per cent of women have suffered a migraine, making it one of the most common disabling conditions around the globe.
Studies using various neuroimaging techniques have shown that migraines are not caused by the constriction and dilation of blood vessels, but rather they begin as a problem of brain excitability.
And the female brain has an 'intrinsic excitability that predisposes them to migraines,' according to researchers.
Dr Andrew Charles, director of the Headache Research and Treatment Programme at the University of California, believes women have a faster trigger than men for activating the waves of brain activity thought to underlie migraines, the Daily Mail reported.
Dr Charles said that migraines show cortical spreading depression (CSD), when dramatic waves of activity spread across the surface of the brain.
This triggers not only the pain of a migraine but the visual symptoms, nausea, dizziness and difficulty concentrating so common in sufferers.
Dr Charles and fellow researcher Dr Kevin Brennan used imaging techniques to visualise the initiation and spread of CSD in mice.
Female mice showed a significantly lower threshold for CSD when compared with males. In other words, it was much easier to evoke the waves of brain activity believed to underlie migraine in females than it was in males.
"The results were very clear. The strength of the stimulus required to trigger CSD in males was up to two or three times higher than that required to trigger the response in females," said Dr Charles.
A variety of factors may reduce the CSD threshold in both sexes, making them more susceptible to migraines. These include genes, hormones and environmental triggers such as stress, diet, changes in sleep patterns and a host of others.
While it is known that migraines in females fluctuate with the menstrual cycle and are more frequent during the menstrual period, Dr Charles said his results appear to be independent of a specific phase of the cycle.
"We didn't monitor the estrous cycle in the female mice, so it's likely we sampled from different estrous phases in different animal," he said.
"Yet we still found a consistent difference in the CSD threshold between males and females.
"Our results suggest that the female brain has an intrinsic excitability that predisposes them to migraine that may not be simply linked to a specific phase of the menstrual cycle," he added.
But some researchers believe migraines are enflamed by the hormonal fluctuation of a woman's menstrual cycle.
Boys are slightly more likely to experience a migraine than girls, but once a girl begins menstruating, the likelihood of her suffering a migraine rockets.
This is blamed on estrogen, although other hormones are also thought to be a trigger.
Dr Jan Lewis Brandes, of the Nashville Neuroscience Group, told NPR.org: "We've begun to see from researchers that the frequency of migraine attack is linked to permanent changes in the brain, and I think that changes the playing field for patients and those of us who take care of them."