Cannabis legalization in Germany did not cause major changes in cannabis use or driving under the influence

Cannabis legalization in Germany did not appear to cause any changes in cannabis use or driving under the influence of cannabis (DUIC), according to a new study.

Germany legalized cannabis possession and cultivation beginning in April 2024. The study, the first nationwide evaluation of cannabis legalization in a European country, found no significant short-term shift in cannabis use prevalence or in the prevalence of DUIC among cannabis users in Germany following legalization.

While cannabis use in Germany rose from 12.1% to 14.4% in the eight months following legalization, this trend did not significantly differ from Austria. The latter country, neighbouring Germany, which has not legalized cannabis, was used as a control.

Among those who reported using cannabis at least once a month, DUIC decreased slightly from 28.5% to 26.8% (unweighted), with no significant difference compared with Austria. DUIC was most common among daily users, while cannabis combined with alcohol or other drugs was most common among weekly cannabis consumers.

The findings are similar to recently-released research in Canada that showed moderate initial increases in DUIC prevalence among the general population following legalization, while DUIC prevalence among cannabis users in Canada, however, remained stable or even declined. Notably, driving after consuming cannabis in Canada remained stable among past 12-month consumers, with a moderately lower prevalence in 2023 than in 2018.

The new German study is the first to evaluate the short-term impact of cannabis legalization in Germany on both cannabis use and DUIC. Like Canada, Germany applies a per-se THC limit of 2 ng/ml whole blood and ∼2.8 ng/ml blood serum. However, some research has shown that such levels do not necessarily correlate to impairment. A recent study out of the United States argued that cannabis users are being unjustly jailed for allegedly driving under the influence.

A 2024 study in Ontario looking at the effects of edible cannabis on simulated driving and blood THC levels also found that driving impairment was not correlated with blood THC.

In Canada, penalties for driving while impaired by cannabis can include: criminal charges, loss of one’s driver’s licence, vehicle impoundment, and fines. Police can use both oral testing equipment and assessments by Drug Recognition Officers.

Legal limits for THC in the blood and their associated penalties are as follows:

An ongoing study from the University of Saskatchewan that used a driving simulator found that many drivers in the test were impaired by a 10mg edible. The CBC reports that in 2023, 1,594 drivers in Saskatchewan had their vehicles impounded and licences suspended for three days for having THC in their system, up from 76 in 2019.

The lead researcher in the study in Saskatchewan also noted that the vast majority of participants were aware that they were too impaired to drive.

“What I found most surprising was the fact that once our participants had consumed the edibles, they were very much aware that they were not safe to drive,” Alexander Crizzle, the director of the driving research and simulation laboratory and professor in the school of public health at the University of Saskatchewan, told CBC.

“For example, 96 per cent reported that they could not drive safely at 1.5 hours. So that is actually a good thing. We’re quite happy to see that, because if they’re aware they can’t drive, they’re probably less likely to do it.”