A guided digital intervention to reduce cannabis use: The ICan randomized controlled trial

Abstract

AbstractAimsTo test the effectiveness of a digital intervention to reduce cannabis use (ICan) with adherence‐focused guidance compared with educational cannabis information.DesignThis was a single‐blind randomized controlled trial. Follow‐up clinical outcome measurements took place 3 and 6 months after randomization.SettingThe trial was conducted in the Netherlands. The intervention and guidance took place on‐line, with recruitment via Facebook/Instagram advertisement campaigns.ParticipantsInclusion criteria were ≥ 18 years, cannabis use on ≥ 3 days/week, the desire to reduce/quit cannabis and using a smartphone. Participants were allocated to either ICan (n = 188) or control (n = 190) (69% male, mean age = 27.5 years).Intervention and comparatorICan is a mobile (web‐)application based on motivational interviewing and cognitive behavioural therapy and includes three main components: screening, brief intervention (six modules) and referral to treatment. The control condition consisted of non‐interactive educational cannabis information.MeasurementsPrimary outcome was the number of cannabis use days in the 7 days prior to the 6‐month follow‐up measurement. Secondary outcome measures at 3‐ and 6‐month follow‐up were the number of grams of cannabis used and attitudes towards seeking professional help for cannabis use related problems.FindingsIntention‐to‐treat analysis showed that 6 months after randomization the mean number of cannabis use days in the past 7 days was reduced in both conditions (time P < 0.001), with no significant group × time interaction effect [ICan = 4.17 days, control = 4.31 days, Cohen's dbetween = 0.06, 95% confidence interval (CI) = −0.15, 0.26, P = 0.93]. Three months after randomization the mean number of grams used in the past 7 days was reduced in both conditions, with a significantly larger reduction in the ICan condition (P = 0.009, Cohen's dbetween = 0.15). At 6‐month follow‐up the significant group × time interaction effect was no longer present (P = 0.30). In both conditions, attitudes towards seeking professional help remained virtually unchanged over time.ConclusionsA digital intervention to reduce cannabis use (ICan) was more effective than non‐interactive educational cannabis information in reducing grams of cannabis used over 3 months, but not more effective at reducing cannabis use days at 6‐month follow‐up. Cannabis use reductions were maintained in both conditions between 3 and 6 months’ follow‐up.