How do trigger factors acquire the capacity to precipitate headaches?

This study tested two contrasting theories of how trigger factors acquire t he capacity to precipitate headaches. The sample consisted of 110 participa nts, of whom 48 suffered from regular headaches. Participants were exposed to a validated headache trigger factor for one of five exposure durations. The trigger used was "visual disturbance" (flicker, glare and eyestrain) in duced by a very bright, stroboscopic light. Response to the stimulus was me asured by participant ratings of the degree of visual disturbance and head pain caused by the stimulus. As expected, the headache sufferers experience d more visual disturbance and head pain in response to the stimulus than th e non-headache individuals. Longer exposure to the stimulus was associated with a subsequent reduction in pain ratings in response to the stimulus. Th is desensitization effect supported an avoidance model of how trigger facto rs acquire the capacity to precipitate headaches. The findings of this stud y have implications for the etiology of headache disorders. Also, the findi ngs imply that the traditional clinical advice that the best way to prevent migraine and headache is to avoid the factors that trigger them, may be co unterproductive, as any short-term gains may be more than wiped out by decr eased tolerance for the trigger factors. (C) 2001 Elsevier Science Ltd. All rights reserved.