The Endorphin Theory
Activation of the body’s natural opioid system: Considerable research supports the claims that acupuncture releases opioids, naturally occurring chemicals in the brain, that may reduce pain or induce sleep. These chemicals may explain acupuncture’s pain-relieving effects.
As mentioned above, one theory that attempts to explain the “how” of acupuncture is the endorphin theory. Studies have shown that acupuncture leads to the release of endorphins and these are powerful natural pain killers.
Some studies, however, have shown no release of endorphins during treatment. The Endorphin Theory view, even if the sole “how” of acupuncture, would only explain effects on pain and perhaps inflammatory related conditions but would be difficult to explain how it may help with anxiety or fertility or parkinsons.