Nocebo: the psychologic induction of pain.

More than two-thirds of an unselected sample of 34 college students reported mild headaches when told that a (nonexistent) electric current was passing through their heads. These reports appeared independent of whether the instructions emphasized the headache-producing effect of the current or whether the emphasis was on a perceptual task, with headache as only a possible side effect. The results are consistent with a view of pain as localized stress. They provide additional grounds for the suspicion that clinical focusing on pain may itself be a cause of pain.