From the Marshall project, on an article in the Los Angeles Times:

Five sentences 101 words, and a tragically erroneous medical conclusion. A new report traces the origins of our opioid epidemic — at least 200,000 Americans have died from prescription drug overdoses — to a 1980 letter to the editor in the New England Journal of Medicine in which the authors concluded “that despite widespread use of narcotic drugs in hospitals, the development of addiction is rare in medical patients with no history of addiction.” The conclusion led to widespread prescriptions of painkillers we now know are highly addictive. 

A related article is here:  The other victims of the opioid epidemic.