Cephalalgia 1998;18 Suppl 22:2-7. Oslo. ISSN 0800-1952 Why is migraine so common?

found that headache is the most common pain symptom that brings a patient to a family physician. In a telephone survey in the USA, about 93 % of people were found to have had a headache in the previous 12 months, and about two-thirds had had a headache in the previous month. In Canada (1), we were able to establish, using a telephone questionnaire with modified International Head-ache Society (illS) criteria, that of a population of 20 million about 3.2 million had migraine and about 5.8 million had tension headache. So, about 9 million people, or 40 % of the Canadian population, suffered from headache. The prevalence for migraine specifically is about 18 % for females and 5 % for males in the USA (2). In Canada, the figures were 13 % for females and 8 % for males (1). Why is migraine such a common condition? The biological nature of migraine The reason that headache is common is because it is part of the human estate, a component of the standard biological equipment. There are several strands of evidence for this. First, from the epidemiological viewpoint it is ubiquitous: studies in any part of the world, including China, Japan