Jeremy Howick, Ioannidis et al.: "Most healthcare interventions tested are not effective according to high quality evidence: a systematic review and meta-analysis"

In this large sample of 1567 drugs, interventions studied...effects of most interventions (94%) interventions were not supported by high quality evidence.

“Patients, doctors, and policy makers should consider the lack of high-quality evidence supporting the benefits and harms of many interventions in their decision-making.”

SOURCE:

Most healthcare interventions tested in Cochrane Reviews are not effective according to high quality evidence: a systematic review and meta-analysis

“Of 1567 eligible interventions, 87 (5.6%) had high quality evidence on first-listed primary outcomes, positive, statistically significant results and were rated by review authors as beneficial. Harms were measured for 577 (36.8%) interventions, 127 of which (8.1%) had statistically significant evidence of harm. Our dependence on the reliability of Cochrane author assessments (including their GRADE assessments) was a potential limitation of our study.”