Luxembourg’s cannabis reform changed driving risks more than the market

In 2023, Luxembourg partially legalised cannabis, permitting home cultivation and private-domain use. The current study aimed to evaluate the short-term impacts of this reform on consumption patterns, market dynamics, product potency, and cannabis-related driving-under-the-influence cases (DUI). An interdisciplinary approach was applied, combining data from cannabis seizures, wastewater analysis, toxicological data from DUI cases, and a WEB-based survey among adults who indicated to have used cannabis in the past 12 months. Indicators were compared before and after the policy change. Most indicators suggested a limited overall impact of partial legalisation in the year following the reform. Tetrahydrocannabinol (THC) concentrations in seized herbal and resin samples remained stable, as did THC metabolite loads in wastewater. Results of the WEB-based survey indicated little change in patterns of use, prices, or acquisition channels, with most survey respondents continuing to purchase from illicit sources. Only a minority of respondents reported personal or intended future cultivation. In contrast, cannabis-related DUI cases increased significantly. Although average THC concentrations in blood samples remained unchanged, elevated levels of THC metabolites suggested a potential increase in chronic use among some individuals. Partial cannabis legalisation in Luxembourg appears to have had only moderate impacts on market dynamics, patterns of use, and product potency during the first year, but was associated with an increase in cannabis-related DUI cases. Similar to findings in other countries, new initiation of cannabis consumption was limited, while people with an established pattern of frequent use may have intensified their use. These findings highlight the need for continued monitoring of impaired driving, cannabis consumption patterns, and emerging trends in self-cultivation, alongside public education on health risks.