Efficacy of a digital intervention to reduce or stop cannabis use : study protocol for a randomized controlled trial

Introduction
Heavy cannabis use is associated with adverse effects on physical and mental health. In France, one in 5 past year cannabis user has tried to quit unsuccessfully in the last 12 months. Digital interventions offer opportunities for cannabis users willing to stop or reduce their consumption, but who are reluctant to seek physical help or are geographically far from a specialised health facility. A personalised 5 week e-coaching program has been designed and developed in a multimodal perspective, in association with other services such as helpline, peer forums and chat services.
Objectives
The main aim of the study is to assess the efficacy of the cannabis app in helping to stop or reduce cannabis use. The secondary objective is to analyse the mechanisms and contextual conditions of this cannabis app efficacy.
Method
The study design is a randomised controlled trial (RCT) including an intervention group and a control group (access to a leaflet with basic information about the harmful effects of cannabis). A total of 560 participants will be included. Data will be collected using online questionnaires sent to participants at the start of the study, after the intervention and 3 months later. Participants aged 18 or over, willing to stop or reduce their current cannabis consumption will be recruited mainly through the drogues-info-service.fr website managed by Santé publique France, where drug users or their relatives can get information or help. Partners and community-based associations working with drug users will also be invited to encourage recruitment. The main outcome will be the number of joints smoked in the last 7 days, 3 months after the end of the intervention. Secondary outcomes will be the number of joints after the intervention, the number of days with cannabis consumption within the past 7 days at 3 months, the satisfaction and perceived utility of the app. A logistic regression will be carried out to estimate an OR (95% CI) for efficacy. A multivariate analysis will explore the influence of users’ characteristics (sex, age, socio-professional category, cannabis dependence, motivation to reduce, quitting experiences) and contextual factors (including conditions of use of the app) on the results.
Discussion
The RCT will provide important insights into the efficacy of an e-coaching app with a multimodal approach.