While it has been argued that addiction is not a unified concept (Karasaki, Fraser, Moore, and Dietze, 2013), perhaps the most widely used definition by medical professionals and addiction researchers is drawn from the diagnostic and statistical manual of mental disorders (DSM). This manual has undergone numerous revisions that reflect changes in how addiction is defined and understood. Drawing on the current DSM criteria (American Psychiatric Association, 2013), for the purpose of this chapter the term "addiction' will connote problematic and compulsive engagement in an activity. The activity to which one is addicted may be drug use, and the harms may be apparent.¹ However, the activity may be something less stigmatized such as work, sex, internet use, or eating,² and (even in the case of drug use) it may be more difficult in some cases to decipher the degree to which the compulsion is problematic or "harmful'.