Belief that commonly-used means effective

Don’t assume a health action is helpful or safe based on how widely used it is.

Things we do for our health (health actions) that have not been properly researched in fair comparisons, but that are widely used or have been used for a long time are often assumed to work. Sometimes, however, they may not be helpful and may even be unsafe.


Research has found that some commonly used health actions might not work or are harmful resulting in doctors changing or ‘reversing’ their recommendations. It is difficult to know exactly how many current health actions are no better than, or are worse than, doing nothing or doing something else that is simpler or less expensive. However, one review of articles about currently used health actions found that about 40% of current medical treatments were not helpful or not safe and about 40% were beneficial. This concept is important not only because people may take health actions that are not helpful, or that are harmful, but also because money is wasted on treatments that do not work.


Bloodletting, taking blood from a patient to prevent or cure illness, was the most common treatment performed by physicians and surgeons for almost two thousand years. In addition to not being helpful, bloodletting was not safe. People were killed from blood loss, including George Washington, the first president of the U.S. Bloodletting could also lead to severe or even fatal infections.

Medicine to reduce heart rhythm abnormalities is a more recent example of a widely-used treatment that was deadly. Because heart rhythm abnormalities are associated with an increased risk of early death after a heart attack, it was believed that medicines that reduced these abnormalities would also reduce early deaths. These medicines were used for many years before it was discovered that they increase the risk of sudden death. At the peak of their use in the late 1980s, they may have been killing as many as 70,000 people every year in the U.S. alone.

Remember: Just because a health action is widely used or has been used for a long time, it does not mean the health action works or does not have harms.

Educational resources for this concept

Primary school


Secondary school




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