Only one in ten medical treatments are backed by high-quality evidence

The conversation September 2, 2020

When you visit your doctor, you might assume that the treatment they prescribe has solid evidence to back it up. But you'd be wrong. Only one in ten medical treatments are supported by high-quality evidence, our latest research shows.

The analysis, which is published in the Journal of Clinical Epidemiology, included 154 Cochrane systematic reviews published between 2015 and 2019. Only 15 (9.9%) had high-quality evidence according to the gold-standard method for determining whether they provide high or low-quality evidence, called GRADE (grading of recommendations, assessment, development and evaluation). Among these, only two had statistically significant results - meaning that the results were unlikely to have arisen due to random error - and were believed by the review authors to be useful in clinical practice. Using the same system, 37% had moderate, 31% had low, and 22% had very low-quality evidence.

The GRADE system looks at things like risk of bias. For example, studies that are "blinded" - in which patients don't know whether they are getting the actual treatment or a placebo - offer higher-quality evidence than "unblinded" studies. Blinding is important because people who know what treatment they are getting can experience greater placebo effects than those who do not know what treatment they are getting.