This article reviews studies evaluating the relationship between endorphins and major depressive disorder. People suffering from depression have been found to have lower levels of beta-endorphins. Results were limited by methodological differences. Alternatives to antidepressants that may increase beta-endorphin levels have been examined. This included exercise, acupuncture and electroconvulsive therapy. Each of these modalities has been shown to increase beta-endorphin levels, although the results have been inconclusive. Additional research is needed to better define the relationship between these modalities and endorphin levels. Introduction Animal and human research studies illustrate the contribution of central opioid systems in major depressive disorder (MDD). The most common endogenous opioid is beta-endorphin (Hegadoren, 2009). Low plasma levels of beta-endorphin lead to depressive symptoms. Many people with MDD do not fully respond to traditional antidepressant medications. Effective alternatives to medications, including exercise, electroconvulsive therapy, and acupuncture, help relieve depressive symptoms by increasing plasma levels of beta-endorphin. Background Information Opioid neuropeptides were first discovered in 1974 by two individual groups of researchers. John Hughes and Hans Kosterlitz were studying the brain of a pig and discovered a small amino acid molecule, enkephalin (Hughes, 1975). Shortly after, Rabi Simantov and Solomon Snyder discovered endporphins in calf brains, short for endogenous morphine. Beta-endorphin is a molecule of a C-terminal fragment of 31 amino acids produced in the pituitary gland and the arcuate nucleus of the hypothalamus. It is found throughout the body, including...... middle of article ......service use and social morbidity associated with depressive symptoms in the community. JAMA 1992; 267 (11): 1478-83Li, CH Proc Natl. Acad. Sci.Public Health Reports (NIMH and NIDA interagency team studies how acupuncture works.) (1974-), Vol. 95, n° 5 (September - October 1980), pp. 503-504 Wilson, Ronald W. and Elmassian Bonnie J., The American Journal of Nursing, Vol. 81, no. 4 (April 1981), pp. 722-725 Terman, M, Terman JS, Quitkin FM, et al. Light therapy for seasonal affective disorder: a review of effectiveness. Neuropsychopharmacology 1989; 2 (1): 1-2 Unutzer J, Patrick DL, Simon G, et al. Depressive symptoms and health service costs among HMO patients aged 65 and older: a 4-year prospective study. JAMA 1997; 277 (20):1618-2Prince, Raymond, Ethos, Vol. 10, n° 4, issue devoted to shamans and endorphins (winter 1982), pp. 303-316