The overall objective of the present thesis was to evaluate the efficacy of motivational interviewing (MI) and cognitive behavioral group therapy (CBGT) in the treatment of gambling disorder including comparisons with a no treatment control group. Secondary analyses aimed at investigating the treatments relative sensitivity to contemporary alcohol problems, as well as investigating processes in MI.
A total of 150 problem gamblers according to NORC DSM-IV screen for gambling problems were randomized to MI, CBGT, or a no-treatment control. MI and CBGT combined in one single treatment arm (participants receiving either MI or CBGT) showed better treatment outcomes than the no-treatment control at post treatment. However, supplementary analyse that only included participants with severe gambling problems (gambling disorder) reviled that the no treatment control showed marginally better outcomes than CBGT and significantly better outcomes than MI.
A secondary analysis was conducted aiming to investigate whether screening for risky alcohol habits can provide guidance on whether people with gambling disorder should be recommended MI or CBGT. The interaction between treatment and alcohol habits was significant and suggests that patients with gambling disorder and risky alcohol habits were better helped by MI, while those without risky alcohol habits were better helped by CBGT.
An additional secondary analysis was conducted with the purpose to test hypothesized relationships among process and outcome variables in the MI theory, in a context of gambling disorder treatment. The Motivational Interviewing Treatment Integrity Code was used to assess therapists’ verbal behaviors during MI sessions and the Client Language Assessment in Motivational Interviewing was used to assess clients’ verbal behaviors. As hypothesized, high scores on empathy reduced symptoms of gambling disorder at six-month follow-up. High scores on MI spirit increased the frequency of preparatory change talk, which in turn increased the probability of commitments occurring. Unexpectedly, MI adherent utterances decreased the frequency of preparatory change talk. No indirect effects were found to confirm that client language mediated the relation between therapist skills in MI and treatment outcome.