Endorphins, Exercise, and Addictions: A Review of Exercise Dependence

Endorphins are endogenous opioids released from the pituitary gland that are believed to mediate analgesia, induce euphoria, and play a role in the reward system in the brain. It has been suggested that endorphins are responsible for creating the relaxed psychological state known as runners high. Studies examining the relationship between vigorous exercise and blood plasma endorphin levels have produced conflicting results. Some indicate a significant increase of endorphins during or after exercise while others do not. Inconsistent methods and experimental techniques have made it difficult to determine a relationship between exercise and endorphin elevations. Research has shown that opioidergic activity plays a role in addictions by mediating the development of reinforcing qualities of certain activities and substances. A newly-established condition known as exercise dependence defines exercise as an addiction, characterized by a compulsion to exercise excessively even when the consequences are harmful to an individuals health, family relationships, and personal wealth (Griffiths, 1997; Hausenblas and Downs, 2002; Loumidis and Wells, 1998). Various surveys and questionnaires have been validated for determining the level of an individuals dependence on and need for exercise. As researchers define a clear relationship between vigorous exercise and increased endorphin levels, causes of exercise dependence can be more concretely determined. Exercise dependence is not currently recognized by the DSM-IV, but its presence in certain human behaviors (similar to those of alcoholics and drug addicts) indicate that it should be precisely defined.