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Current state of research - Potential and risks of cannabis use

On 27 November 2017 the result report was published of the study ‘Cannabis: Potential and risks. A scientific analysis (CaPRis)’, which was funded by the Federal Ministry of Health. The study was performed under the leadership of Privat-Dozentin Dr. rer. nat. Eva Hoch from the Department of Psychiatry and Psychotherapy at the LMU Hospital in Munich and Privat-Dozentin Dr. rer. nat. Miriam Schneider from the Institute for Developmental Psychology and Biological Psychiatry at the University of Heidelberg. It summarises the current state of research on cannabis.

The study evaluated all relevant data and research papers published in German and English in the last ten years. It presents both the risks of using cannabis to get high and the benefits of cannabinoids for medical use.

‘We are seeing astonishingly rapid progress in the scientific knowledge about the effects of cannabinoids, the constituent of the hemp plant Cannabis sativa’, said Privat-Dozentin Dr. Eva Hoch. Together with her research group and 30 national and international experts, the head of the meta-study evaluated more than 2000 scientific studies.

‘In the last ten years we have seen a particularly significant increase in the amount of scientific literature addressing the risks of using cannabis to get high’, reported Dr. Eva Hoch. The study reveals a detailed picture of the different risks of acute and chronic use. It found clear reductions in memory performance, attention and psychomotor skills. Physically, cannabis can have negative effects on respiratory function and the circulatory system (e.g. heart attack and hypertension). Cannabis use is also associated with lower educational achievement and can cause dependence. Risks are greater in case of early onset of use in adolescence, intensive use and co-use with tobacco.

As regards medical use of cannabis, the study found a benefit in the indication ‘nausea and vomiting or appetite stimulation’ in people receiving chemotherapy for cancer or people with HIV/AIDS and a slight improvement in the symptoms of chronic pain. Studies also found that the spasticity associated with multiple sclerosis improved. For many other diseases, statements on the efficacy of cannabis cannot yet be made because of the limited data available.

The Drug Commissioner of the Federal Government, Marlene Mortler, stated: ‘In the public debate, the consequences of using cannabis to get high are often downplayed. So far, the possibilities for medical use have been limited to certain indications. In both areas I am interested in looking at things in a clear and realistic way: especially for children and adolescents it really is dangerous to smoke cannabis regularly. The development of cannabis dependence is not uncommon, the risk for mental illnesses, such as depression, anxiety disorders and psychoses, increases. This is true at least until the completion of brain development in the early 20s. Cannabis as a medicine is another topic: medicinal cannabis can ease the nausea and loss of appetite in patients with cancer or HIV. It can also reduce pain slightly in patients with chronic pain. Such effects have not been proven for various other illnesses that are currently being discussed. We definitely need to put a lot more effort into informing people about the dangers of cannabis use and improving the medical care of people addicted to cannabis.’

The complete study report, including a detailed presentation and discussion of the results, is about 500 pages long and will be published soon by a scientific publisher (Springer).

The result report, which contains the key messages of the study, can be found on the website of the BMG (in German):

We have prepared podcasts with answers to common questions about the results of the study.


Priv.-Doz. Dr. rer. nat. Eva Hoch