EACH YEAR, ABOUT 1 million people in the U.S. have stents put in to treat clogged coronary arteries — a procedure some may not have needed, according to a study released Monday. Although stents relieve angina, they were found to be no more effective in eliminating the risks of heart attack, stroke or death than drug treatment alone.

Americans want to believe that modern medicine is sophisticated and evidence-based, but this study underscores how little we know when we make most medical decisions. Some of the pills and medical devices we depend on are used on the basis of evidence that is flimsy at best.

Read the full op-ed on the Los Angeles Times website.