Testing the Effects of Cann'App, a Digital Intervention for Cannabis Harm Reduction

"PF comprises the following content:~* Self-reported PBS questionnaire, personalized feedback on PBS, possibility to select strategies to start using or use more often, possibility to set a reminder to use PBS strategies.~* Short questionnaire on cannabis use (frequency/number of hours under the influence) and normative feedback on participant's cannabis use as compared to people of same age and gender in the general population and among Cann-L participants.~* Question on money spent for cannabis purchase, personalized feedback (total amount spent and corresponding number of grams of cannabis over one year), gamified gauge to picture potential yearly savings, reflection on how to use the saved money, and possibility to set a reminder for money saving objectives.~* Questionnaire on cannabis-related consequences, feedback on the level of consequences met, question about which consequence(s) participant might want to think about, and possibility to set a reminder to think about consequences."

"Two-task intervention including:~1. Counterfactual thinking:~ * Description of a recent negative situation related to cannabis use encountered by the participant~ * Identification of a preventive strategy that would have addressed this situation~ * Writing a sentence formatted as If only +preventive strategy, then + description on how the specific past problem would have improved~ * Assessment of participant's intention and confidence in using the preventive strategy~ * Imagining a future situation using this preventive strategy~ * Possibility to set a reminder of the preventive strategy.~2. Episodic future thinking:~ * Description of a significant positive event that might occur in the short-term (3 months) and that does not involve cannabis use~ * Assessment of the importance and enjoyment of this positive event~ * Encouragement to imagine it as vividly as possible~ * Suggestion to describe the positive event in detail and to write it down~ * Possibility to set a reminder of the positive event."

"SFAS includes:~* A questionnaire on how participant value different aspects of their life, and feedback on valued domains.~* Two open-ended questions on short- and long-term life goals.~* A questionnaire assessing time allocation (hours per week allocated to different activities, e.g. socializing, working, etc.), and personalized feedback including the time spent using substances and recovering from their effects.~* Gamified exercise to imagine allocating time in a different way.~* List of substance-free recreational activities in the region of Lausanne, with possibility to select activities on a wish-list including internet hyperlinks.~* Possibility to set a reminder of the selected activities.~* Single-item questionnaire on stress and mood, and feedback on stress and mood level.~* Open-ended question on coping strategies currently used for stress and mood.~* List of coping strategies that can be selected.~* Possibility to set a reminder of stress/mood coping strategies."

Minimal intervention (Control Intervention), consisting of simple, text-only web pages containing information on cannabis effects and health-related risks, cannabis consumption modes, cannabis harm reduction and protective behavioral strategies, as well as hyperlinks to additional resources and online help.