Cognitive and emotional factors in placebo analgesia

Information that a painkiller has been administrated induces an expectancy of reduced pain, and the expectancy has been shown to reduce pain. This is termed placebo analgesia. We hypothesized that an expectancy of reduced pain reduces stress.

The present study (N=84) investigated this hypothesis. To further study the effects of stress and emotions on pain, we provided information about the pain stimulus to half the subjects. Pain was induced by the submaximum tourniquet technique.

Expectations and pain information both decreased pain to the same degree, but independently, and only in males. Lower pain was not related to subjective stress, cortisol, or circulating beta-endorphin. All experimenters were women, and the finding of placebo analgesia only in males fits well with findings that males report less pain to female experimenters.

Placebo analgesia is not related to stress and is influenced by the social context in which pain is recorded.