(from the chapter) Although the majority of individuals who gamble report no significant financial consequences associated with their gaming, an estimated 0.4-5.3% worldwide have a problematic or pathological form of gambling behavior (Bakken, Gotestam, Grawe, Wenzel, & Oren, 2009; Cunningham-Williams, Cottler, Compton, & Spitznagel, 1998; Odlaug & Grant, 2010; Petry & Armentano, 1999; Shaffer, Hall, & Vander Bilt, 1999; Toce-Gerstein, Gerstein, & Volberg, 2009; Wardle et al., 2007). According to the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5), gambling disorder or "pathological" gambling (PG) is defined by a repetitive engagement in gambling behavior resulting in significant financial, occupational, and/or psychosocial dysfunction (American Psychiatric Association, 2013). For these individuals, a multitude of viable and efficacious therapeutic interventions have been developed. Understanding the clinical characteristics of these individuals may aid the clinician and researcher in the advancement of existing and new treatment approaches for this population. Current treatment for PG involves a number of different options-inpatient treatments; intensive outpatient, individual, and group Cognitive Behavior Therapy (CBT); and pharmacotherapy- which have all demonstrated benefit in treating gambling disorders (Hodgins et al., 2011; Pallesen, Mitsem, Kvale, Johnsen, & Molde, 2005). Although there is currently no agreed-upon standard of care for disordered gambling, the most widely studied treatment for PG has been some form of CBT (Table 57.1). A meta-analysis identified 22 randomized trials published between 1968 and 2004 (Pallesen et al., 2005). This meta-analysis revealed that in general, psychological treatments were more effective than no treatment at both posttreatment (overall effect size = 2.01) and at followup averaging 17 months later (overall effect size = 1.59) (Hodgins et al., 2011). A more recent meta-analysis that included 25 studies (Gooding & Tarrier, 2009) found that although there was considerable variability in the outcomes reported, posttreatment effects were generally positive for different types of therapy (e.g., behavioral, cognitive) and mode of therapy (e.g., individual, group, self-directed). To date, there are no randomized trials of inpatient treatment (Hodgins & Holub, 2007). These studies show that CBT is beneficial for gambling disorders, but many questions remain. Which form of CBT is best, and for whom? There have been no comparison studies of the different manualized forms of CBT, and so one cannot make recommendations at this time regarding which approach is most effective. Also, no manualized CBT treatment has been examined in a confirmatory study by another independent investigator. The heterogeneity of gambling treatment samples may also complicate identification of effective treatments. What is the optimal duration of therapy? Given the success and low cost of brief interventions, should everyone undergo a brief intervention first and only if they fail that move on to more intensive therapy? What specific components should be included in the CBT program? Which components are most effective? Do certain people respond differently to different CBT components? No study has examined whether certain individuals with gambling disorders would benefit differentially from specific CBT treatments. The matching of different treatment approaches to different subtypes of gambling disorders, based on neurobiology or genetics, may improve treatment outcomes. What role does comorbidity play?