Four more genes that highlight an inherited cause for common migraine trapped by European and Australian scientists on Sunday.
The genetic variants were spotted in a trawl through the DNA code of 4,800 people with a history of "migraine without aura," which accounts for two-thirds of migraine attacks.
But the telltales were absent among more than 7,000 counterparts who did not suffer from these debilitating headaches.
In previous work, researchers uncovered three genes associated with migraine.
But this is the first to find genes not linked to migraine with aura -- the sensation in which patients have the impression of looking through frosted glass.
Migraine affects roughly one woman in six and one man in eight, and is a major cause of work absence.
The precise cause is unknown, but inherited vulnerability as well as environmental triggers are the suspects.
Scientists describe the condition as a brain disorder in which neurons, or brain cells, respond abnormally to stimuli.
Two of the newly-identified genes back the theory that blood vessels, and thus blood flow, play an important part in the process.
The study, published in the journal Nature Genetics, was led by the International Headache Genetics Consortium.