(from the chapter) Gambling is a lucrative industry, with United States casinos reporting annual gross revenues of over $34 billion (American Gaming Association, 2012). The vast majority of individuals who gamble do so for recreation and report no significant financial consequences or any difficulties controlling their behavior. Some people (estimated to be 0.4%-5.3% worldwide; National Opinion Research Center, 1999; Petry, 2005; Shaffer, Hall, & Vander Bilt, 1999), however, develop a maladaptive form of gambling behavior associated with impaired functioning, reduced quality of life, and high rates of bankruptcy and divorce. This form of gambling behavior has been defined by the American Psychiatric Association in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) as being a Gambling Disorder (APA, 2013). For individuals with Gambling Disorder, several promising therapeutic interventions have been developed (Stea & Hodgins, 2011). Although recognized by both Emil Kraepelin (1856-1926) and Eugen Bleuler (1857-1939), disordered gambling behavior was first officially recognized in DSM-III as pathological gambling (Black & Grant, 2013). The condition has not received substantial empirical investigation until relatively recently. The disorders was categorized as one of the impulse-control disorders not elsewhere classified, along with disorders such as kleptomania, pyromania, and trichotillomania. In DSM-5, the disorder is included in the chapter on substance use disorders because of consistently high rates of comorbidity, similar presentations of some symptoms, and genetic and physiological overlap.