A pilot study by the University of Augsburg and the Bezirkskliniken Schwaben indicates an increase in mental health problems and psychosis caused by cannabis – since legalization on April 1, 2024. The study, published in the German Medical Journal, analyzed hospitalization rates in Bavarian Swabia and observed a relevant increase.

In the two years before legalization from April 2022, mental health problems caused by cannabis were treated less frequently than in the first year after that until the end of March 2025. Cases of general cannabis-related mental disorders increased one-and-a-half times, while cannabis-induced psychoses were almost doubled. The total number of inpatient treatments remained stable. The proportion of cannabis-induced psychoses in psychotic disorders from the schizophrenia spectrum increased from 4.7 percent to 8.2 percent.

The six clinics cover psychiatric care for around 1.9 million inhabitants in the administrative district of Swabia, including Augsburg. The anonymous evaluation is based on routine data and was carried out as part of the German Center for Mental Health. This is the first study on this connection in a German region.

A causal relationship with legalization cannot be proven with certainty. Possible influences include increased diagnostic attention, less stigmatization and thus more openness on the part of those affected, or expectations among medical staff. Longer observation periods are needed to evaluate transitions from cannabis-induced psychosis to chronic disorders.

The results plead for further research and increased prevention. In addition to general campaigns on the risks of cannabis use, vulnerable groups such as adolescents and people with pre-existing mental illnesses should be specifically informed about psychosis risks. The risk increases with THC content and frequency of use.

Original Paper:

Frequency of psychotic illnesses after cannabis legalisation – Deutsches Ärzteblatt

Editor: X-Press Journalistenbüro GbR

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