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.

For example, anti-arrhythmic drugs were widely prescribed in the belief that they would reduce heart attack deaths until a clinical trial found that they actually increased the risk of death.

In another example, putting infants to sleep on their stomach was recommended based on expert opinion that babies would be less likely to choke on their vomit until large studies found that stomach sleeping increased the risk of SIDS.