How the opioid crisis became the biggest drug epidemic

Every day brings another story about the depth of the country’s opioid crisis. A rise of pain killer prescriptions from doctors and a pharmaceutical industry eager to boost sales in the 1990s sparked a wave of addiction that shot up by almost 500 percent in the last 15 years. As a prologue to our series covering the opioid crisis, “America Addicted,” William Brangham reports on how we got here.