Testing the Effects of Cann'App, a Digital Intervention for Cannabis Harm Reduction
Cann'App
Testing the Effects of a Digital Intervention for Cannabis Harm Reduction - The Cann'App Fractional Factorial Randomized Controlled Trial
2 other identifiers
interventional
565
1 country
1
Brief Summary
The goal of this clinical trial is to learn if a digital web application can prevent the risks related to cannabis use among adult regular cannabis users who are enrolled in a pilot trial for cannabis sales regulation conducted in Lausanne, Switzerland (i.e., Cann-L study) and have agreed that their data were used in other studies. The main question it aims to answer is: Do participants who have access to the intervention modules of the web application raise their use of protective behavioral strategies to lower cannabis-related risks? Researchers will compare the intervention modules to a control module (i.e., information on cannabis-related risks and harm reduction) to see if the web application works to prevent the risks related to cannabis use. They will also compare intervention modules across each other to see whether one works better than another. Participants will:
- Create a user account in the web application
- Access the web application using a laptop, tablet or smartphone
- Use the web application as they wish throughout the duration of the study
- Complete the regular Cann-L study questionnaires every six months, which will be used to measure their cannabis use and related risks.
Trial Health
Trial Health Score
Automated assessment based on enrollment pace, timeline, and geographic reach
participants targeted
Target at P75+ for not_applicable
Started Jan 2026
1 active site
Health score is calculated from publicly available data and should be used for screening purposes only.
Trial Relationships
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Study Timeline
Key milestones and dates
First Submitted
Initial submission to the registry
August 27, 2025
CompletedFirst Posted
Study publicly available on registry
September 5, 2025
CompletedStudy Start
First participant enrolled
January 5, 2026
CompletedPrimary Completion
Last participant's last visit for primary outcome
July 1, 2027
ExpectedStudy Completion
Last participant's last visit for all outcomes
August 1, 2027
January 12, 2026
January 1, 2026
1.5 years
August 27, 2025
January 8, 2026
Conditions
Keywords
Outcome Measures
Primary Outcomes (1)
Frequency of Protective Behavioral Strategies for Marijuana Use as Measured by the PBSM-17 Short Form Scale
This outcome will be measured using the Protective Behavioral Strategies for Marijuana Use (PBSM-17) Short Form scale, a self-reported 17-item questionnaire measuring the frequency of PBS for cannabis use on a 6-point Likert scale ranging from 1 (never) to 6 (always).
This outcome will be assessed at 1- and 7-month follow-up.
Secondary Outcomes (2)
Cannabis Use Frequency
This outcome will be measured at 1- and 7-month follow-up.
Number of Hours High on a Typical Day
This outcome will be measured at 1- and 7-month follow-up.
Other Outcomes (6)
Cannabis Use Disorder Severity as Measured by CUDIT-R
This outcome will be measured at 1- and 7-month follow-up.
Cannabis Purchase Task
This outcome will be assessed at 1- and 7-month follow-up.
Source of Cannabis Supply
This outcome will be assessed at 1- and 7-month follow-up.
- +3 more other outcomes
Study Arms (5)
Condition 1 - Personalized Feedback + Information
EXPERIMENTALAccess to "Personalized Feedback" module (PF, Study Intervention) and "Information" module (Minimal, Control Intervention)
Condition 2 - Imagine the future + Information
EXPERIMENTALAccess to "Imagine the Future" module (IMAGIN, Study Intervention) and "Information" module (Minimal, Control Intervention)
Condition 3 - Substance-Free Activities Session + Information
EXPERIMENTALAccess to "Substance-Free Activities Session" module (SFAS, Study Intervention) and "Information" module (Minimal, Control Intervention)
Condition 4 - Full Intervention + Information
EXPERIMENTALAccess to the full intervention (PF+IMAGIN+SFAS) and "Information" module (Minimal, Control Intervention)
Condition 5 - Information only (Control)
ACTIVE COMPARATORAccess to "Information" module (Minimal, Control Intervention)
Interventions
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.
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.
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.
Eligibility Criteria
You may qualify if:
- Eligible participants will be those included in the pilot trial of cannabis sales regulation in Lausanne, Switzerland (Cann-L study).
- being adult (\>18 years old),
- having current cannabis use (i.e., use at least once a month over the last 6 months)
- living in the city of Lausanne. To enter the study, they complete an entry assessment verifying their age and proof of residence, and confirming that they have current cannabis use.
You may not qualify if:
- being younger than 18 years old,
- being pregnant or breastfeeding,
- having a health condition contraindicating the use of cannabis (e.g., severe psychiatric disorder).
- The consent to participate in the Cann-L parent trial comprises an option to be contacted to participate in sub-studies, including studies on prevention measures. All participants having accepted to be so contacted will be proposed to participate in the present study.
- not providing informed consent to participate in sub-studies, including studies on prevention measures,
- not providing informed consent to participate in the present study.
Contact the study team to confirm eligibility.
Sponsors & Collaborators
- Jacques Gaumelead
- Apptitudecollaborator
- Swiss National Science Foundationcollaborator
- Addiction Switzerlandcollaborator
Study Sites (1)
Lausanne University Hospital
Lausanne, Vaud Canton, 1011, Switzerland
MeSH Terms
Conditions
Condition Hierarchy (Ancestors)
Study Officials
- PRINCIPAL INVESTIGATOR
Jacques Gaume, PhD
University of Lausanne Hospitals
Study Design
- Study Type
- interventional
- Phase
- not applicable
- Allocation
- RANDOMIZED
- Masking
- TRIPLE
- Who Masked
- PARTICIPANT, INVESTIGATOR, OUTCOMES ASSESSOR
- Masking Details
- The randomization will be imbedded within the application, therefore concealment of allocation will be total. Participants will be blind to their experimental condition. Research staff involved in the study will not be informed of participants' group allocation. All study assessments will be done electronically. The generation of the randomization sequence and its programing into the study website will be conducted by the developing team who will not have contacts with participants or any involvement in the study implementation and analyses.
- Purpose
- PREVENTION
- Intervention Model
- FACTORIAL
- Sponsor Type
- OTHER
- Responsible Party
- SPONSOR INVESTIGATOR
- PI Title
- PhD scientist
Study Record Dates
First Submitted
August 27, 2025
First Posted
September 5, 2025
Study Start
January 5, 2026
Primary Completion (Estimated)
July 1, 2027
Study Completion (Estimated)
August 1, 2027
Last Updated
January 12, 2026
Record last verified: 2026-01
Data Sharing
- IPD Sharing
- Will share
- Time Frame
- Beginning immediately after the publication of results and ending 20 years after study termination.
- Access Criteria
- A formal request should be submitted to the Principal investigator and a data sharing agreement must be signed.
The data collected for this study may be reused and/or transmitted for other studies (including abroad), always in coded form (i.e., deidentified dataset). For each instance of reuse in another study, a data transfer agreement will need to be established.