Cannabis use prevalence before and early after partial legalisation in Germany.

Kotz D.; Manthey J.; Klosterhalfen S.; Steinhoff P.; Viechtbauer W. · The International journal on drug policy · 2026

**Background & Methods** This prospective observational study assessed changes in cannabis use prevalence following Germany's partial legalization through the Cannabis Act (CanG) on April 1, 2024. The analysis utilized 23 repeated cross-sectional surveys conducted between April 2022 and March 2026 (approximately 2 years pre- and post-legalization), covering 35,957 respondents aged 14-64 years. Piecewise binomial logistic regression models with random wave effects were employed to detect slope changes in past 12-month cannabis use and heavy use patterns, with sensitivity analyses testing alternate intervention dates. **Key Findings** - Overall cannabis use prevalence remained stable at 6.4% with no statistically significant changes following legalization; slope coefficients post-implementation were non-significant across all analyses (all p ≥ 0.15). - Daily or almost daily (heavy) use among past 12-month users showed no meaningful increase after the law reform, despite a significant pre-legalization downward trend (-0.091, p = 0.04). - Subgroup analyses by gender, age (14-24 vs. 25-64 years), and use patterns demonstrated consistent stability in prevalence across all demographic groups during the early post-legalization period. **Dosage & Administration** Not reported. **Safety & Adverse Effects** Not reported. **Evidence Quality** This study provides moderate-quality evidence with notable strengths including large sample size, repeated measurements over extended periods, and appropriate statistical methodology accounting for clustering. However, significant limitations warrant cautious interpretation: the 2-year post-legalization follow-up may be insufficient to detect delayed population-level effects; reliance on self-reported survey data introduces potential recall and social desirability biases; the study cannot determine whether legalization changed patterns among non-users or addressed illicit market dynamics; and generalizability to other jurisdictions implementing cannabis legalization remains uncertain. The authors appropriately recommend extended monitoring and multi-source data collection, acknowledging that behavioral and epidemiological changes may emerge over longer timeframes. This represents preliminary short-term evidence that early legalization was not associated with rapid increases in cannabis prevalence in Germany.

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