Most of us are familiar with a friend or family suffering from addiction – an estimated one in every 12 adults in the U.S. suffer from alcohol dependency alone. But spotting and defining addiction can get tricky. "The current thinking is that addiction and addiction-related issues are on a continuum. So they go from completely non-existent to very severe and all the gradations along the way," says Dr. Wilson Compton, deputy director of the National Institute on Drug Abuse. He says that addiction tends to be very obvious when it's severe but that the boundaries between a bit of partying, problematic use, and full-blown addiction are blurry. Even the classic symptoms of withdrawal and tolerance may not necessarily signal an addiction. Core features actually tend to be more behavioral, says Compton, involving different ways people adjust their lives to accommodate their substance use. This is why those checklists you find online or help centers can be so misleading. Compton helps us take a fair look at the signs of addiction, what they mean, and how to know when there really is a problem.