The German cannabis experiment: The first study results are here

For the study, the Center for Interdisciplinary Addiction Research at the University Hospital Hamburg-Eppendorf evaluated around 77,000 hospital admissions between January 2022 and September 2025. It was created as part of the “Ekocan” research project financed by the Federal Ministry of Health, which has been monitoring the consequences of partial legalization from the beginning.

Since April 1, 2024, adults in Germany have been allowed to legally possess and grow cannabis. At the same time, the rules for prescribing medical cannabis were relaxed. Shortly after the law came into force, the number of admissions due to cannabis use rose slightly – by 5.6 percent for adults (from 1.12 to 1.27 per 1,000 hospital admissions), and by 14.9 percent for adolescents (from 1.07 to 1.22). In absolute numbers, this corresponds to 1,359 additional admissions for adults and 91 for juveniles in the first year after legalization.

While the value for adults remained permanently at the new level, the situation for young people returned to normal: after 35 weeks, the initial increase was mathematically offset.

Level remains high

Admissions for two diagnoses rose particularly sharply. The number of cannabis poisonings among adults increased by 37.1 percent immediately after legalization (from 0.08 to 0.11 per 1000 shots) – that’s 392 additional cases over a year. Cannabis-induced psychoses were even more common: here the rate rose by 16.4 percent (from 0.32 to 0.40), which corresponds to 980 additional admissions. In both cases, the rate subsequently stabilized at the increased level.

Ursula Havemann-Reinecke sees the data as a clear indication that “partial legalization has not led to a reduction in the number of cannabis intoxications or psychoses” – contrary to what Lauterbach or supporters of the law had hoped. They had relied on controlled quality and better information.

The number of unreported cases could be higher

The professor of addiction medicine at Göttingen University Medical Center told the Science Media Center (SMC) that the number of unreported cases could be even higher: Children and young people with cannabis poisoning are often not treated in psychiatric hospitals but in children’s hospitals, and accordingly they do not even appear in the billing data on which the study is based. The same applies to adults who were treated internally instead of psychiatrically. Mixed consumption, for example with alcohol, is also not taken into account in the evaluation.

The study provides two possible explanations for the increase in admissions. On the one hand, it is conceivable that legalization has lowered inhibitions and encouraged more people to try cannabis. On the other hand, many users may have switched to so-called medical cannabis.

This is also easily available for recreational purposes, but is significantly stronger than cannabis from illegal sources: According to the study authors, the THC content is on average 24 percent for medical cannabis and around 15 percent for “street cannabis”. THC, i.e. tetrahydrocannabinol, is the most important psychoactive ingredient in the cannabis plant – the substance that causes the high.

The higher the THC content, the greater the risk of poisoning, psychosis and anxiety, says Alkomiet Hasan, professor of psychiatry at the University of Augsburg. However, further studies must show whether the increase in hospital admissions is actually primarily due to the switch to medical cannabis.

A signal after two years

Hasan does not find the results surprising – similar developments are known from other countries, he tells the SMC. He also points out a possible bias effect: Due to the current debate, doctors may ask more often about cannabis use and make the diagnosis accordingly more often. “Even if we take these into account, this issue cannot explain the full extent of the increase.”

It is crucial that a signal appears after just two years, although the observation period is actually still too short “to assess serious complications – such as the transition to schizophrenia or suicides.”

Nevertheless, “they make you sit up and take notice”: 25 additional cases per week may not sound like much, says Hasan, but that would result in over 1,000 per year, some of which could result in serious, permanent mental illness.

Hasan demands consequences: uncomplicated access to medical cannabis via online prescriptions and without personal contact with a doctor is dangerous. Cannabis could be a useful treatment option for certain illnesses, but there is no scientific basis for most mental illnesses.

This is also where the new Health Minister and Lauterbach’s successor comes in: Nina Warken (CDU) wants to tighten the cannabis law and in particular prevent online prescriptions without personal doctor-patient contact. The new figures should give her additional arguments for this.