Acupuncture relieves pain by releasing endorphins, the body's natural pain-killing chemicals, and by affecting the part of the brain that governs serotonin, a brain chemical involved with mood control. The acupuncturist typically inserts 4 to 10 needles and leaves them in place for 10 to 30 minutes while you rest. A usual course of treatment includes six to 12 sessions over a three-month period.