Cannabis use prevalence before and early after partial legalisation in Germany

BACKGROUND: On April 1st, 2024, Germany implemented the Cannabis Act (CanG), allowing adults to cultivate and possess recreational cannabis. We assessed whether this was associated with a change in the prevalence of cannabis use. METHODS: A series of 23 repeated surveys between April/May 2022 and March/April 2026 (covering the period approximately two years before and two years after the CanG). We measured past 12-month cannabis use (at least once; daily or almost daily use). Piecewise binomial logistic regression models used wave dates as predictors, allowing a slope change at the first full wave after April 2024, with a random effect for wave. Analyses covered the total sample and subgroups by gender, age (14-24 vs. 25-64 years), and daily or almost daily use among past 12-month users. Sensitivity analyses used alternate intervention dates (in-time placebo tests). RESULTS: Among 35,957 respondents aged 14-64 years, 2302 (6.4%) reported past 12-month cannabis use. The prevalence of cannabis use and proportion of daily or almost daily (heavy) users remained largely stable before and after the law reform. None of the slope coefficients before the introduction of the CanG were statistically significant (all p ≥ 0.07), except for the negative slope in daily or almost daily users in the subgroup of past 12-month users (-0.091, p = 0.04). Also, none of the coefficients for the change in the slope were statistically significant (all p ≥ 0.15). Sensitivity analyses supported these findings. CONCLUSIONS: Germany's 2024 cannabis reform was not associated with changes in 12-month use prevalence or heavy use early (two years) after implementation. Continued monitoring over longer periods and across multiple data sources is recommended, as effects may emerge later.