@Article{info:doi/10.2196/27463, author="Baumgartner, Christian and Schaub, Michael Patrick and Wenger, Andreas and Malischnig, Doris and Augsburger, Mareike and Walter, Marc and Berger, Thomas and Stark, Lars and Ebert, David Daniel and Keough, Matthew T and Haug, Severin", title="CANreduce 2.0 Adherence-Focused Guidance for Internet Self-Help Among Cannabis Users: Three-Arm Randomized Controlled Trial", journal="J Med Internet Res", year="2021", month="Apr", day="30", volume="23", number="4", pages="e27463", keywords="cannabis; common mental disorders; adherence; social presence; internet; cognitive behavioral therapy; motivational interviewing; therapy; mental health; mental disorder; guidance; self-help; drug abuse; randomized controlled trial", abstract="Background: Despite increasing demand for treatment among cannabis users in many countries, most users are not in treatment. Internet-based self-help offers an alternative for those hesitant to seek face-to-face therapy, though low effectiveness and adherence issues often arise. Objective: Through adherence-focused guidance enhancement, we aimed to increase adherence to and the effectiveness of internet-based self-help among cannabis users. Methods: From July 2016 to May 2019, cannabis users (n=775; male: 406/575, 70.6{\%}, female: 169/575, 29.4{\%}; age: mean 28.3 years) not in treatment were recruited from the general population and were randomly assigned to (1) an adherence-focused guidance enhancement internet-based self-help intervention with social presence, (2) a similar intervention with an impersonal service team, and (3) access to internet as usual. Controls who were placed on a waiting list for the full intervention after 3 months underwent an assessment and had access to internet as usual. The primary outcome measurement was cannabis-use days over the preceding 30 days. Secondary outcomes included cannabis-dependence severity, changes in common mental disorder symptoms, and intervention adherence. Differences between the study arms in primary and secondary continuous outcome variables at baseline, posttreatment, and follow-up were tested using pooled linear models. Results: All groups exhibited reduced cannabis-use days after 3 months (social presence: --8.2 days; service team: --9.8 days; internet as usual: --4.2 days). The participants in the service team group (P=.01, d=.60) reported significantly fewer cannabis-use days than those in the internet as usual group; the reduction of cannabis use in the social presence group was not significant (P=.07, d=.40). There was no significant difference between the 2 intervention groups regarding cannabis-use reduction. The service team group also exhibited superior improvements in cannabis-use disorder, cannabis-dependence severity, and general anxiety symptoms after 3 months to those in the internet as usual group. Conclusions: The adherence-focused guidance enhancement internet-based self-help intervention with an impersonal service team significantly reduced cannabis use, cannabis-use disorder, dependence severity, and general anxiety symptoms. Trial Registration: ISRCTN Registry ISRCTN11086185; http://www.isrctn.com/ISRCTN11086185 ", issn="1438-8871", doi="10.2196/27463", url="https://www.jmir.org/2021/4/e27463", url="https://doi.org/10.2196/27463", url="http://www.ncbi.nlm.nih.gov/pubmed/33929333" }