Abstract: Fourteen studies (n = 1245) met the inclusion criteria. Eleven studies compared CBT with control and comparisons at 0 to 3 months post-treatment showed beneficial effects of therapy that ranged from medium (when defined by financial loss from gambling: SMD -0.52; 95% confidence interval (CI) -0.71 to -0.33, n = 505) to very large (for gambling symptom severity: SMD -1.82; 95% CI -2.61 to -1.02, n = 402). Only one study (n = 147) compared groups at 9 to 12 months follow-up and produced smaller effects that were not significant. Four studies of motivational interviewing therapy were identified and mainly considered samples demonstrating less severe gambling (relative to studies of pathological gamblers). Data suggested reduced financial loss from gambling following motivational interviewing therapy at 0 to 3 months post-treatment (SMD -0.41; 95% CI -0.75 to -0.07, n = 244), although comparisons on other outcomes were not significant. The effect approached zero when defined by gambling symptom severity (SMD -0.03; 95% CI -0.55 to 0.50, n = 163). Studies compared groups at 9 to 12 months follow-up and found a significant effect of motivational interviewing therapy in terms of frequency of gambling (SMD -0.53; 95% CI -1.04 to -0.02, n = 62), with comparisons on other outcomes that were not significant. Two studies of integrative therapies also considered samples demonstrating overall low gambling severity, and found no significant effects of therapy at 0 to 3 months post-treatment. Comparisons at 9 to 12 months follow-up suggested a medium effect from therapy in terms of gambling symptom severity, with no significant differences for other outcomes. One study (n = 18) considered another psychological therapy (i.e.Twelve-Step Facilitated Group Therapy) and suggested beneficial effects in terms of most outcomes at 0 to 3 months post-treatment. The evidence supporting these various classes of therapy ranged from very low to low quality. This review supports the efficacy of CBT in reducing gambling behaviour and other symptoms of pathological and problem gambling immediately following therapy. However, the durability of therapeutic gain is unknown. There is preliminary evidence for some benefits from motivational interviewing therapy in terms of reduced gambling behaviour, although not necessarily other symptoms of pathological and problem gambling. However, the findings are based on few studies and additional research is needed to inform conclusions. There is also evidence suggestive of some possible benefit from integrative therapies, and other psychological therapies for pathological and problem gambling. However, there are too few studies and evidence is insufficient to evaluate these therapies. The majority of studies in this review varied in risk of bias, and much of the evidence comes from studies with multiple limitations. The current data may thus reflect overestimates of treatment efficacy.

Plain-language summary: Psychological therapies have been proposed for the treatment of pathological and problem gambling, and this review summarised current evidence for these therapies. It included best-quality randomised trials, where therapy was compared with conditions including 'no treatment’ controls or referral to Gamblers Anonymous. It considered categories of therapy including: (1) cognitive-behaviour therapy (CBT); (2) motivational interviewing therapy; (3) integrative therapy; and (4) other psychological therapy. The search identified 14 studies and we combined data from these. Data from nine studies indicated benefits of CBT in the period immediately following treatment. However, there were few studies across longer periods of time (e.g. 12 months) after treatment, and little is known about whether effects of CBT are lasting. Data from three studies of motivational interviewing therapy suggested some benefits in terms of reduced gambling behaviour, but not necessarily other symptoms of pathological and problem gambling. However, the data come from few studies and conclusions regarding motivational interviewing therapy require further research. There were also few studies that provided evidence on integrative therapies (two studies) and other psychological therapies (one study), and there is currently insufficient data to evaluate the efficacy of these therapies