Allowing stress to build up is so dangerous that even relaxation following heightened stress can act as a trigger for migraine attacks, a new research indicates.

"This study demonstrates a striking association between reduction in perceived stress and the occurrence of migraine headaches," said Richard B Lipton, director, Montefiore Headache Center in New York.

To examine what triggers headaches, the researchers conducted a three-month electronic daily diary study which captured 2,011 diary records and 110 eligible migraine attacks in 17 participants.

The study compared levels of stress and reduction in stress as predictors of headache.

"Results were strongest during the first six hours where decline in stress was associated with a nearly five-fold increased risk of migraine onset," Lipton added.

The hormone cortisol, which rises during times of stress and reduces pain, may contribute to the triggering of headache during periods of relaxation.

"This study highlights the importance of stress management and healthy lifestyle habits for people who live with migraine," said Dawn C Buse, director of behavioural medicine at Montefiore Headache Center.

People should attempt to relax during periods of stress rather than allowing a major build up to occur, Buse added.

This could include exercising or attending a yoga class or may be as simple as taking a walk or focusing on one's breath for a few minutes, said the study that appeared in the journal Neurology.