Conditioned response models of placebo phenomena: further support.

Following our earlier research, we further investigated a model that conceptualizes placebo phenomena as the result of conditioning and attempted to extend and replicate the finding that placebo responses can be conditioned in human subjects. Two groups of 10 subjects were told that they were receiving an analgesic which was in fact a placebo. During the conditioning, placebo administration was surreptitiously paired with an increase in the painful stimulus for half of the subjects and with a decrease for the other half. Subjects were tested pre and post conditioning for a placebo response. A second type of experimental pain was also used to determine stimulus generalization. The results confirmed a previous finding that placebo responses can be conditioned in human subjects. The implications for clinical practice of a learning model of placebo behavior are discussed.