Brief mindfulness intervention for adults with cannabis use disorder: A randomised clinical trial.

Background: Cannabis use disorder (CUD) is characterised by strong cravings and an inability to reduce cannabis use despite experiencing adverse psychosocial outcomes. Brief, accessible, scalable, and low-cost interventions are needed to support people with a CUD. We investigated if a brief mindfulness-based intervention (MBI) reduces cannabis frequency, quantity and craving, compared to both an active and passive control conditions. Methods: A pre-registered, double-blind randomised control trial was run in in 66 adults (19 female) aged 18-56 with CUD reporting attempts to cut down or quit in the past 2 years, recruited from the general community (October 2019-July 2022). Participants were 1:1:1 allocated, to one of 3 interventions; MBI (n = 23), Relaxation (n = 21) or Control (n = 22) with a mean duration of 16 days, stratified by age and sex. All conditions included daily monitoring of usage. Baseline and follow-up in person testing occurred in Melbourne, Australia. The intervention occurred online. The primary outcome was change in cannabis use days (Delta follow-up minus baseline). Secondary outcomes were changes (Delta follow-up minus baseline) in: cannabis grams and craving (visual analogue scale; VAS), mindfulness (Five-Facet Mindfulness Questionnaire) and relaxation (VAS). We carried out intention-to-treat analysis. Results: There were no significant intervention-by-time effects on the primary outcome - cannabis frequency (F=0.26, FDRp = .86)-nor on secondary outcomes: quantity, cravings, relaxation or mindfulness. Conclusion: Based on these findings a brief MBI does not appear to help people with CUD reduce their cannabis use. Trial Registration: ISRCTN Registry Identifier: ISRCTN76056942 (Mapping short-term brain changes in cannabis users). Submission date: 28/04/2020. Registration date: 12/05/2020. The interventions are described below and here: ISRCTN76056942 https://www.isrctn.com/ISRCTN76056942 (DOI: https://doi.org/10.1186/ISRCTN76056942). The pre-registered hypotheses and analysis plan can be found here: https://osf.io/sfjwk.