Endorphins and Major Depressive Disorder

This paper reviews the studies evaluating the relationship between endorphins and Major Depressive Disorder. Individuals with depression were found to have lower levels of beta-endorphins. The findings were limited by methodological differences. Alternatives to antidepressants that potentially increased beta-endorphin levels were reviewed. This included exercise, acupuncture, and electroconvulsive therapy. Each of these modalities was shown to increase beta-endorphin levels although the results were not conclusive. More research is needed to better define the relationship between these modalities and endorphin levels.

Introduction

Animal and human research studies illustrate the contribution of the central opioid systems in Major Depressive Disorder (MDD). The most common endogenous opioid has been found to be beta-endorphin (Hegadoren, 2009). Low levels of plasma beta-endorphin lead to depressive symptoms. Many individuals with MDD do not respond completely to traditional anti-depressant medications. Effective alternatives to medications, including exercise, electroconvulsive therapy, and acupuncture, help to alleviate depressive symptoms through increasing plasma beta-endorphin levels.

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 found a small amino acid molecule, enkephalin (Hughes, 1975). Soon after, Rabi Simantov and Solomon Snyder discovered endporphins in the calf brain, short for endogenous morphine.

Beta-endorphin is a molecule of 31-amino acid C-terminal fragment which is produced in the pituitary gland and hypothalamic arcuate nucleus. It is found throughout the body includi...

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