A Self-Guided Internet-Based Intervention for the Reduction of Gambling Symptoms A Randomized Clinical Trial

IMPORTANCE Most individuals with problem gambling or gambling disorder remain untreated due to barriers to treatment. Limited research exists on alternative treatments. OBJECTIVE To investigate the efficacy of a self-guided internet-based intervention for individuals with gambling problems and to identify potential outcome moderators. DESIGN, SETTING, AND PARTICIPANTS This single-center randomized clinical trial was conducted from July 13, 2021, to December 31, 2022, at the University Medical Center Hamburg-Eppendorf. Participants were recruited across Germany for 2 assessments (before intervention [t0] and 6 weeks after intervention [t1]). Eligible participants were individuals aged 18 to 75 years with gambling problems, internet access, German proficiency, and willingness to participate in 2 online assessments. INTERVENTION The self-guided internet-based intervention was based on cognitive behavioral therapy, metacognitive training, acceptance and commitment therapy, and motivational interviewing. MAIN OUTCOME AND MEASURES The primary outcome was change in gambling-related thoughts and behavior as measured with the pathological gambling adaption of the Yale-Brown Obsessive-Compulsive Scale. Secondary outcomes were change in depressive symptoms, gambling severity, gambling-specific dysfunctional thoughts, attitudes toward online interventions, treatment expectations, and patient satisfaction. RESULTS A total of 243 participants (154 [63.4%] male; mean [SD] age, 34.73 [10.33] years) were randomized to an intervention group (n = 119) that gained access to a self-guided internet-based intervention during 6 weeks or a wait-listed control group (n = 124). Completion at t1 was high (191 [78.6%]). Results showed a significantly greater reduction in gambling-related thoughts and behavior (mean difference, -3.35; 95% CI, -4.79 to -1.91; P < .001; Cohen d = 0.59), depressive symptoms (mean difference, -1.05; 95% CI, -1.87 to -0.22; P = .01; Cohen d = 0.33), and gambling severity (mean difference, -1.46; 95% CI, -2.37 to -0.54; P = .002; Cohen d = 0.40) but not in gambling-specific dysfunctional thoughts (mean difference, -1.62; 95% CI, -3.40 to 0.15; P = .07; Cohen d = 0.23) favoring the intervention group. Individuals in the intervention group who had a positive treatment expectation and more severe gambling-specific dysfunctional thoughts and gambling symptoms benefited more on the primary outcome relative to the control group. CONCLUSIONS AND RELEVANCE In this randomized clinical trial, the effectiveness of a self-guided internet-based intervention for individuals with self-reported problematic gambling behavior was demonstrated when measured 6 weeks after start of the intervention. The study's findings are particularly relevant given the increasing need for accessible and scalable solutions to address problematic gambling.