The effectiveness of a web-based intervention for Japanese adults with problem drinking: An online randomized controlled trial

AIMS: This study aimed (1) to delineate how a web-based intervention affects the problem drinking behaviors of Japanese adults and (2) to examine the moderating effects of disorder levels and alcohol outcome expectancies on intervention outcomes. METHODS: We implemented an online two-armed parallel-group randomized controlled trial with 546 Japanese adults. Adults aged 20 years or older and who scored eight or higher on the Alcohol Use Disorder Identification Test were included in this study. Participants were randomly allocated to the intervention group or the waitlist/control group. The intervention comprised assessment of drinking behavior, personalized normative feedback, psychoeducation about the consequences of problem drinking, and a short quiz. The outcomes were weekly drinking quantity and abstinent days, largest drinking quantity in one day, and alcohol-related consequences reported at baseline and at one-, two-, and six-month follow-ups. A mixed-effects model regression was conducted to compare the intervention and control groups. RESULTS: The attrition rates at each follow-up were 52.93%, 49.45%, and 32.60%, respectively. The time × condition interaction effect on weekly drinking quantity was significant at the two- and six-month follow-ups, d = 0.28, 95% CI [0.04, 0.51], d = 0.34, 95% CI [0.05, 0.63], respectively. Moderations related to the intervention effect were not statistically significant. CONCLUSION: A web-based intervention was found to be effective for two and six months only on drinking quantity measures of Japanese adults with problem drinking. Limitations including high drop-out rates in are discussed.