GUEST POST by David A. Mark
Placebos don’t work when you are asleep. Or if you have Alzheimer’s disease. But they do seem to make a difference in research and clinical practice, as I found when preparing a recent article for Nutraceuticals World.
In clinical trials for subjectively reported symptoms such as pain or mental state, the placebo effect is roughly 30%. But the average varies from condition to condition. For chronic fatigue syndrome or Crohn’s disease. the average reported improvement across multiple clinical trials was 20%; for osteoarthritis it was 40%.
And for any of the nearly dozen conditions tabulated for the article, the range from trial to trial was large. In 20 studies of bipolar mania, the average was a 31% improvement in the placebo groups, but the range was from 9% to 59%.
The placebo effect is impacted by variables in the design and conduct of clinical trials. For example, a larger placebo effect was reported when subjects had higher expectations of being successfully treated, or if the trial itself was larger, longer, or had more visits per trial. Use of the opiate antagonist naloxone reverses placebo-induced pain relief, suggesting production of endogenous opioids as a mechanism
At the medical practice level, the worst-case scenario is a charismatic doctor who invents or champions a novel treatment (or surgical procedure) – and then writes a book. The certainty of the healer-researcher raises expectations in the patients, leading to positive results. Sports performance products are also subject to a strong placebo effect.
The lesson? Testimonials and open-label trial results should never be provided as sole evidence of efficacy when a product marketing campaign is challenged by a regulatory authority.
David A. Mark, Ph.D., is president of dmark consulting LLC, a science consulting company serving the dietary supplement and functional food industry. Contact him at email@example.com or 978-897-0890.