Post for some research. I’ll be adding to this later.

http://www.medicinenet.com/script/main/art.asp?articlekey=55001

Endorphins interact with the opiate receptors in the brain to reduce our perception of pain and act similarly to drugs such as morphine and codeine. In contrast to the opiate drugs, however, activation of the opiate receptors by the body’s endorphins does not lead to addiction or dependence.