The United States is in the grip of an unprecedented public health crisis—one in which well-meaning doctors have played a part. Between 1999 and 2014 sales of prescription opioid drugs nearly quadrupled. In 2012 alone, physicians issued 259 million opioid prescriptions—enough to give a bottle of pills to every adult in the country. And in 2015 more than half of all overdose deaths in the U.S. involved opioids—either pain medications, such as OxyContin and Vicodin, or illicit substances, such as opium and heroin. To put that statistic in perspective, opioids claimed roughly as many lives that year as car crashes.