More Hospital Stays Due to Cannabis Since Partial Legalization: Study Sees Evidence of Increased Risk

For the study, the Center for Interdisciplinary Addiction Research at the University Medical Center Hamburg-Eppendorf evaluated around 77,000 hospital admissions between January 2022 and September 2025. According to the data, hospital admissions due to cannabis use rose shortly after the law came into force by 5.6 percent among adults and by as much as 14.9 percent among adolescents. In absolute numbers, this corresponds to 1,359 additional admissions among adults and 91 among adolescents in the first year after legalization.

Numbers in Detail: Intoxications and Psychoses

The increase is even more pronounced for cannabis-related intoxications. Among adults, the rate shot up by 37.1 percent immediately after legalization, from 0.08 to 0.11 per 1,000 admissions. Extrapolated, this corresponds to roughly 392 additional cases per year. Overall, the researchers recorded around 1,500 additional hospital stays in the first year, most of them due to intoxications and psychoses.

Particularly striking is the development in cannabis-induced psychoses. Here, the rate rose by 16.4 percent from 0.32 to 0.40 per 1,000 hospital admissions, which mathematically corresponds to 980 additional admissions. Alkomiet Hasan, co-author of the study, described the figures as "relevant." "Wer an Psychosen leidet, hört oft Stimmen oder hat Wahngedanken," explained Stefan Gutwinski, senior physician at the Clinic for Psychiatry and Psychotherapy at Berlin's Charité.

Possible Causes of the Increase

The authors cite several possible causes for the increase. First, it is conceivable that, as a result of legalization, more people had decided to try cannabis because the threshold of inhibition had fallen due to the removal of penalties. Second, prescription cannabis on average contains around 24 percent THC, while the concentration on the street market is around 15 percent. "Da der Konsum von Cannabis mit mehr als zehn Prozent oder 15 Prozent THC mit einem erhöhten Risiko für psychische Probleme verbunden ist, kann der Umstieg auf Medizinalcannabis selbst für erfahrene Konsumierende sowie für Patientinnen und Patienten ein Risiko darstellen," the study states.

At the same time, the researchers warn against overinterpreting the results. Hasan acknowledged that 25 additional cases per week might "sound little," but emphasized: "Selbst ein moderater Anstieg, wie hier beschrieben, hat immense gesellschaftliche Konsequenzen." Over the years, some of the cases could develop into severe mental illnesses such as schizophrenia. The observation period is also actually still too short to reliably assess severe complications.

Reactions from the Research Community

Ursula Havemann-Reinecke sees in the data a clear indication "dass die Teillegalisierung nicht zu einer Senkung der Zahl von Cannabisintoxikationen oder Psychosen geführt hat" – contrary to what was hoped by the then Health Minister Karl Lauterbach and other proponents of the law. "Selbst wenn wir diese in Betracht ziehen, kann dieser Sachverhalt nicht den gesamten Umfang der Zunahme erklären." 25 additional cases per week correspond to more than 1,000 per year.

Differences Between Adults and Adolescents

A differentiated picture emerges for adolescents. Although the number of admissions rose briefly by 14.9 percent immediately after the law came into force, it mathematically normalized again after 35 weeks. Among adults, however, the value remained permanently at the new level. In absolute numbers, 91 additional admissions among adolescents were recorded within one year, an increase of 3.9 percent.

The study was produced as part of the "Ekocan" research project funded by the Federal Ministry of Health, which scientifically accompanies the consequences of partial legalization. It joins a growing number of analyses that put Germany's cannabis course to the test. An evaluation published in April already concluded that Germany has "den größten prinzipiell legal-kommerziellen Markt" for medical cannabis in Europe.

How quickly this market is growing is demonstrated by trade figures. In 2025, 200 tonnes of medical cannabis were imported legally and commercially into Germany, an increase of 198 percent compared to 2024. Experts including Jakob Manthey from the University Medical Center Hamburg-Eppendorf and University Medical Center Leipzig had analyzed data from more than 70,000 hospital admissions. In the year after the law came into force, 1,395 more adults were admitted to hospital due to cannabis than before.

Limitations of the Study

The study authors point out that there are several factors in their analysis that could distort the data. For example, it is possible that patients with cannabis-related complaints have been more likely to seek hospital treatment since legalization because they no longer feared criminal consequences. A changed diagnostic practice or improved documentation in hospitals could also have influenced the statistics.

Despite these limitations, the researchers consider their findings to be a serious signal. "Das ist relevant," said Hasan. Scientists had already warned before partial legalization that the number of psychoses could rise. The current figures appear to at least partially confirm this warning – albeit with the caveat that long-term consequences such as schizophrenia or suicides can only be reliably assessed with a significantly longer observation period.

Overall, the study thus paints a mixed picture of partial legalization. On the one hand, the feared increase among adolescents has so far not solidified. On the other hand, the additional hospital stays among adults are not a temporary phenomenon but have persisted for two years. For the political assessment of the law, the new data are therefore likely to play an important role.

The researchers call for the developments to continue to be closely monitored and for prevention services to be expanded. In particular, the increased THC content in medical cannabis and its easier availability also for non-medical use must be examined more closely. Whether the cannabis law in its current form will endure depends not least on how upcoming studies confirm or weaken the trend observed so far.

What is certain: around 1,500 additional hospital stays in a single year are not a marginal phenomenon. They touch on questions of public health, hospital care capacities, and not least the political responsibility for a law that was introduced primarily with the argument of better control and reduced health risks.