Doctors and patients (and anyone who pays for healthcare) — need to know that medical treatments are safe and effective, but it’s an open secret in the medical field that not all treatments, including ones that are commonly used, are safe and effective.

Only one in 20 medical treatments have high-quality evidence to support their benefits, according to a recent study. The study also found that harms of treatments are measured much more rarely (a third as much) as benefits.