Sher L.
Med Hypotheses. 1998 Jun;50(6):475-8.

Abstract
Ancient and contemporary papers report that acupuncture and its variations have a considerable effect on psychological state and behavior. Evidence from experimental and clinical studies suggests that acupuncture and its variations exert a strong influence on endogenous opioids in the brain, and that the endogenous opioid system is involved in various mental functions. The author suggests that the endogenous opioid system can play the key role in the mediation of the effects of acupuncture and its variations on mood, behavior, learning, and memory. Clinical implications of this suggestion are discussed.