Objective: Migraine and Tension-type headaches are common and disabling disorders, but their pathophysiologies are poorly understood. Dysfunctional pain inhibition is postulated to contribute to the development and/or maintenance of these disorders. Offset analgesia, a temporal contrast effect which activates brain structures involved in pain modulation, has never been assessed in headache sufferers. The object of the study was to compare the offset analgesia effect in a group of headache sufferers to a group of healthy controls.
Methods: Undergraduate college students (N=111) were recruited through a research participant pool, and were compensated for their participation with research credit. Participants provided demographic and inclusion/exclusion information, and completed a diagnostic interview for headache disorders. Next, participants established their pain threshold for a temperature stimulus. This temperature was used in the offset analgesia procedure in which participants were asked to continuously rate a series of 3 temperatures: 5 seconds at pain threshold, 5 seconds at 1 degree Celsius above pain threshold, and 15 seconds at pain threshold.
Results: Participants with headaches reported an average of 41 headaches a year, with the most common diagnosis being Frequent Episodic Tension-type (30%), followed by Migraine (26%), Infrequent Episodic Tension-type (9%), and Mixed (7%). Although offset analgesia was observed, t (99) = 3.54, p < .01, there was no significant difference in the degree of offset analgesia when healthy controls were compared to those with migraine or tension-type headache, F (2, 88) = 1.17, p = .31. Degree of offset analgesia also did not differ as a function of headache frequency, r < 0.04, n=76, p=.96.
Conclusions: The current study demonstrated offset analgesia in a sample of young adults, and provides the first evidence that this form of pain modulation is not associated with headache symptoms. It should be noted, however, that differences may yet be observed in a clinical population with more severe and/or prolonged headache history.