Smoke a joint and the day is your friend? The Bundestag is expected to vote on the cannabis law next week. According to the Traffic Light Coalition’s plans, cannabis cultivation and consumption should be permitted for adults within set limits from April – and so many a stoner’s dream could come true in Germany.

The idea still remains controversial. It’s less about the goal of stopping dealers. Almost everyone wants that. But medical concerns arise as to whether young people are sufficiently aware of the risks of cannabis. The brain matures by the age of 25. Anyone who disrupts this process by smoking weed heavily can suffer lifelong consequences – keyword psychosis.

“I fear that with the planned law we will cast out the devil with Beelzebub,” says Euphrosyne Gouzoulis-Mayfrank. The neurologist and psychiatrist is the future president of the German Society for Psychiatry and Psychotherapy (DGPPN). Age is the crucial point in this discussion. This is not seen enough.

Risky consumption has many factors

Cannabis is a psychoactive substance from the hemp plant that can be addictive – whether packaged as a joint, hash cookie or otherwise. “Risky consumption cannot be identified across the board,” says Stephanie Eckhardt, head of the addiction prevention department at the Federal Center for Health Education (BZgA). There are factors that interact: How often is cannabis used? How much of it? And how high is the THC content, i.e. the concentration of the drug tetrahydrocannabinol?

Cannabis consumption has increased in Germany, especially among young adults between the ages of 18 and 25, reports Eckhardt. Almost half of them have now consumed cannabis, she says, referring to data from 2021. There are only assumptions about the increase: availability, the social environment, social trends and also the price on the black market. According to the Federal Ministry of Health, around 4.5 million adults in Germany used cannabis at least once in 2022 – most often between the ages of 18 and 24.

Manipulation in the brain

According to the planned law, cannabis should remain banned until people reach the age of majority. Then there is a step model: 30 grams per month would be legal for 18 to 21 year olds in Germany, 50 grams would be legal for all older adults. “This is no longer unproblematic recreational consumption,” says Gouzoulis-Mayfrank, chief physician at the LVR Clinic in Cologne. 50 grams a month was enough for several joints a day. Even 30 grams is too much for young adults. “The planned legalization is a field test in society,” says the doctor for the DGPPN. “From our point of view, we shouldn’t move forward quite so recklessly at the moment.”

Researchers are thinking about the body’s own system for cannabinoid molecules: there are naturally structures and docking points for these substances in the brain. Among other things, they regulate appetite, emotions and the sensation of pain. This complex system matures slowly in humans until their mid-20s. If cannabis is added from outside, this process can be disrupted. Doctors assume that frequent smoking of weed in adolescents shifts and changes the cannabinoid structures in the brain – and that this manipulation can have effects throughout life.

Increased risk of psychosis

There is evidence for this from various research strands, explains Gouzoulis-Mayfrank. Anyone who smokes weed early and a lot has a significantly increased risk of psychosis – even many years later. Another consequence of this could be a greater susceptibility to all kinds of addictions. Federal Health Minister Karl Lauterbach (SPD) is also aware of the risks. Cannabis is particularly damaging to the still-growing brain, he says. He had already emphasized in August that no one should misunderstand the law. “Cannabis consumption is being legalized. It still remains dangerous.” But has this message arrived?

Expert misses clear signal to adults

“In recent years there has been an increasing openness to talk about cannabis, including about the risks associated with its consumption,” says Eckhardt from the Federal Center for Health Education. “It shouldn’t be a taboo topic.” But it also imposes restrictions. “There are opportunities and risks.” The BZgA’s message to young people is therefore: Stop smoking weed. Cannabis is a psychoactive substance that can be addictive.

Psychiatrist Gouzoulis-Mayfrank expects collateral damage in Germany if legalization goes ahead as planned. “I fear that it will not be possible to convey the dangers of cannabis credibly.” That’s why your trade association is only in favor of approval from the age of 21. “This would also send a clear signal to young adults that smoking weed is problematic for them.”

Due to different rules and controls, the effects of legalization can vary from country to country. Experiences from abroad are therefore not always transferable to Germany. In addition to alcohol and nicotine, cannabis is considered the most popular intoxicant worldwide, according to research by the German Center for Addiction Questions.