The Challenges of Evaluating Specific and Nonspecific Effects in Clinical Trials of Acupuncture for Chronic Pain.

The Acupuncture Trialists' Collaboration has updated its individual patient data meta-analysis of acupuncture for chronic pain originally published in 2012. The updated meta-analysis, published in 2018, now includes raw trial data from 39 trials and 20,827 patients. The overall effect of acupuncture, and the effect of sham acupuncture controls, was evaluated. For 4 conditions, acupuncture has statistically significantly better effects than sham acupuncture (effect sizes 0.16-0.19 [small]). When compared with usual care controls, effect sizes are larger (0.44-0.63 [moderate]). Sham acupuncture has a considerable therapeutic effect; true acupuncture compared with usual care has an effect size of around 0.5, of which 60% is ascribed to nonspecific context effects plus sham, and the remaining 40% to the specific benefit of true acupuncture. Investigators also determined no significant variation in effect related to any acupuncture characteristic; that acupuncture's effect size drops against a high-intensity control; and that only 10%-15% of acupuncture's benefit is lost at 12 months post-treatment. Acupuncture is more than a placebo for chronic pain, and both specific and nonspecific effects can be distinguished in a meta-analysis of appropriate size.