The influence of the psyche and the brain on immunity and disease susceptibility: a critical review.

In critically reviewing the sources of evidence connecting psyche and brain with the immune system, the authors include a brief review of current knowledge of the immune system, its interactions with the neuroendocrine system, and other factors influencing its regulation. These include developmental stages, aging, rhythmicity, and a variety of exogenous influences. The need for developing further information about normal base lines is emphasized. Against that background, many sources of data demonstrating connections between the central nervous system and the immune system are presented: indirect evidence from clinical and experimental illnesses involving the immune system, and direct changes in either humoral or cellular immunity after natural or experimental stress, conditioning, hypnosis, and direct brain stimulation. Possible mechanisms are discussed, as well as some important methodological issues for further research.