Known medically as "substance use disorder," addiction is a complex, chronic disease marked by compulsive alcohol/drug use that leads to actual changes in the brain. In other words, addiction involves more than the misuse of alcohol or other drugs. Listen in as host William C. Moyers talks with clinician Christopher Yadron about telltale signs of disease progression—physical, behavioral, social and spiritual indicators. His most important takeaway? Addiction is treatable and help is available.