To the Editor: A frequently overlooked cause of headache is that of caffeine withdrawal. In a recent study, 11 per cent of psychiatric inpatients said that they had had caffeine-withdrawal headaches.1 Such headaches were experimentally induced as early as 1943.2 They have been clinically observed3 and epidemiologically documented to occur in natural settings.4 Headache usually begins approximately 18 hours after the most recent intake of caffeine. Beginning with a feeling of cerebral fullness, it rapidly progresses to a painful and throbbing headache, peaking approximately three to six hours after onset; it is not unusual for the pain to last a. . .
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