Substance abuse is among the major public health concerns of the 20th century. However defined, excessive use of illegal drugs and prescribed medications is an all-too-common societal problem, not only in the United States, but across the globe. The negative effects of excessive substance use influence not only the individuals who use these substances but also their immediate and extended families and society in general. Moreover, illicit substance use is connected to many of the most pressing of our societal ills, including illness, crime, violence, and homelessness.