http://www.sciencedaily.com/releases/2009/08/090810104935.htm Link to abstract at bottom of sciencedaily page. "In the study, researchers at the U-M Chronic Pain and Fatigue Research Center showed acupuncture increased the binding availability of mu-opoid receptors (MOR) in regions of the brain that process and dampen pain signals – specifically the cingulate, insula, caudate, thalamus and amygdala." ""Interestingly both acupuncture and sham acupuncture groups had similar reductions in clinical pain," Harris says. "But the mechanisms leading to pain relief are distinctly different." The study participants included 20 women who had been diagnosed with fibromyalgia, a chronic pain condition, for at least a year, and experienced pain at least 50 percent of the time. During the study they agreed not to take any new medications for their fibromyalgia pain.""