Introduction:
The government in Germany is planning to legalize cannabis, which calls for a close look at the health risks of cannabis use. Cannabis is the most commonly used illicit drug in Germany. In 2021, around 4.5 million people (8.8 percent of the population) have used cannabis in the past year. In the same year, half of 18- to 25-year-olds had ever used cannabis. In Europe, hashish or marijuana is usually smoked and most of the user smoke cannabis mixed with tobacco, exposing them to the health risks of both substances. The aim of the project is to publish information for advocacy communication and provide an overview of current knowledge and gaps in the existing research, to inform and support legislative institutions in their decision making or in the formulation of legislation.

Material and Methods:
A comprehensive non-systematic review of literature to get a survey of scholarly sources about smoking cannabis in combination with tobacco. Sources were scientific online platforms like e.g. PubMed, PNAS, JAMA Network.

Results:
Tobacco and cannabis are often used in combination, so the side effects of each substance are difficult to assign. But many of the compounds formed during the inhalation of smoke are carcinogenic and harmful to the lungs and cardiovascular system whether cannabis or tobacco is consumed. The inhalation technique of cannabis is more intensive, because the volume of the puffs is larger, inhalation is deeper and pulmonary retention time is longer. If both substances are combined, the users are exposed to the same health risks as with tobacco smoking. The combined use of nicotine and cannabis can lead to nicotine dependence and difficulties in quitting both substances. In addition, tobacco smokers may be more likely develop dependence symptoms for cannabis.

Conclusions:
Using cannabis and tobacco in a mixed form increases the risk of addiction, makes it more difficult to reduce both substances and shows all the known risk factors of tobacco use. Therefore, the public should be informed about these health risks and be strongly advised against smoking cannabis.