From the moment that Judith Grisel started drinking alcohol at age 13, she was hooked. For the next ten years, Grisel suffered from addiction, as she used drugs from marijuana to opiates to psychedelics.

As a recovering addict and neuroscientist, Grisel learned that she was especially vulnerable because she was genetically predisposed to addiction. (She is one of many who are susceptible to the disease.) Grisel, a professor of psychology at Bucknell University and the author of “Never Enough: The Neuroscience and Experience of Addiction,” explains the effect of illicit drugs on the brain and what makes them so addictive.