Abstract
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. TRIAL REGISTRATION: bfarm.de Identifier: DRKS00024840.