Are positive alternative medical therapy trials credible?: Evidence from four high-impact medical journals.

Forty-five complementary and alternative medicine (CAM) efficacy randomized controlled trials (RCTs) from high-impact medical journals (NEJM, JAMA, Annals of Internal Medicine, and Archives of Internal Medicine) were reviewed based on their meeting three validity criteria (the existence of a placebo control, moderate attrition rates, and 50 or more participants per group). Of the 26 efficacy trials meeting all three criteria, only 2 (7.7%) were judged to be positive (i.e., the alternative therapy was significantly superior to its placebo control), while over half (55.5%) of the 19 trials that failed to meet one or more of these criteria reported positive results (p < .001). Of the two positive high-validity trials, one was funded and authored by the herbal company marketing the product tested and one used a placebo-control group of questionable credibility. This analysis is consistent with the hypothesis that CAM therapies are no more effective than placebos when adequate experimental control is present.