3. A guided digital intervention to reduce cannabis use: the ICan randomized controlled trial in the Netherland

We evaluated the effectiveness of a digital intervention to reduce cannabis use (ICan) with adherence focused guidance compared to educational cannabis information. We conducted focus groups with the target audience to assess their needs and preferences. The results of the focus groups were used to inform the development of the intervention.

A single-blind randomized controlled trial. Inclusion criteria were ≥18 years; cannabis use on ≥3 days/week; the intention to reduce/quit cannabis and using a smartphone. n=378 participants were randomized (69% male, mean age 27.5 years). The primary outcome was the number of cannabis use days in the 7 days prior to the 6-month follow-up measurement. Secondary outcome measures were the number of grams of cannabis used and attitudes towards seeking professional help for cannabis use related problems.

Intention-to-treat analysis preliminarily showed that six months after randomization the mean number of cannabis use days in the past 7 days was significantly reduced in both the ICan condition and the control condition (p<.001) with no significant difference between conditions (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=.009, Cohen’s dbetween=0.15). At 6-month follow-up the difference between conditions was no longer statistically significant (p=0.30). In both conditions attitudes towards seeking professional help remained virtually unchanged over time.

Our study shows favorable 3-month effects of ICan in reducing grams of cannabis used, but no difference in use days compared to our control condition.

Disclosure of interest: For this study, Trimbos institute received funding from the Netherlands Ministry of Health, Welfare and Sports. No other funding was received for the ICan intervention development nor for the study.