Web-based interventions have the potential to reduce the treatment gap for problem gambling. In the past years, several web-based help options were made available to the public. However, only few studies were conducted to test their effects. This study investigated the efficacy of two interventions for problem gamblers provided online by the German Federal Center for Health Education (BZgA). The first intervention is the guided program "Check Out" (CO), the second is email counselling (EC). A web-based randomized controlled trial with follow-up surveys after 3, 6 and 12 months was conducted. Participants were allocated to CO, to EC or to a waitlist (WL). Outcomes were the degree of problem gambling according to the Problem Gambling Severity Index, the number of days gambled in past 30 days, the highest stake during the past 30 days and the subjective well-being (WHO-5). 167 individuals were included in the trial. In comparison to the WL at the 3 months follow-up, participants of CO showed significant improvements with moderate to strong effect sizes in all outcomes. Strongest effects were found in the problem gambling severity (d = 0.91; p = 0.023), followed by the well-being (d = 0.70; p = 0.011), the gambling days (d = 0.59; p = 0.001) and the highest stake (d = 0.55; p = 0.012). Improvements were sustained until last follow-up. Compared to the WL, users of EC had beneficiary results in the problem gambling severity (d = 0.74; p = 0.022). No significant effect differences were found between CO and EC. However, according to process evaluation, users of CO reported a significantly stronger working alliance than users of EC (d = 0.70; p = 0.019) and used the intervention considerably longer (d = 0.84; p = 0.004). CO helps treatment-seeking individuals to sustainably reduce their gambling behavior and to increase their general well-being. Compared to EC, CO seems a better support option, since its effects include a wider range of outcomes. Possible reasons are the more engaging program structure and elements of CO, as well as the closer interaction between client and counselor.
Keywords: Counseling; Email; Gambling disorder; Pathological gambling; Prevention; Problem gambling.