NOVA joins scientists and sufferers alike as they probe the mysteries of addiction. They are discovering that addiction is not simply a lack of willpower; drug abuse produces significant chemical changes in the brain… changes that are hard to control, and hard to reverse. What’s worse, many addictions start with prescription or even over-the-counter pain killers for entirely legitimate ailments. And it is not just drugs… alcohol, sugar, caffeine, even exercise can incite addictive behaviors. In the midst of the opioid crisis, and in a world in which many other diseases can be traced to addictive behavior, NOVA investigates: how do addictions work? And what can the science of addiction tell us about how we can resolve this dire social issue… and how we shouldn’t.