Cannabis: why do some people have fun and others stress when they smoke?

Man Smoking a Cigarette

While some people have fun smoking cannabis, others suffer from paranoid episodes. This difference in response is believed to be due to genetic variations in the brain.

While more and more countries allow cannabis for therapeutic use and some countries such as Uruguay, the Netherlands, the United States (some states only) and Canada have even authorized it for recreational use, the brain mechanisms involved in marijuana use are still poorly understood.

However, a study published in Scientific Reports on July 5 found out why some people had fun when they smoked while others experienced episodes of paranoia and extreme stress. According to the researchers, genetic variations in a part of the brain called the nucleus accumbens, which plays a central role in the reward circuit, are at stake.

To reach this conclusion, researchers at the Schulich School of Medicine and Dentistry in Canada administered THC, the psychoactive compound of marijuana, to rats and recorded their behaviour and brain activity in the nucleus accumbens, a regional complex responsible for the reward circuit. This region involves two neurotransmitters: dopamine (desire) and serotonin (health and inhibition).

Differences probably due to genetic variations  

When THC is activated in the frontal part of this area, it encourages addictive behaviours in the same way as morphine-type opioids and the experience is great. On the other hand, when THC interacts with the posterior zone of the nucleus accumbens, the emotional symptoms are similar to those observed in schizophrenics, the researchers note.  The latter therefore identified a region in the rat brain that appears to "independently control the addictive properties of cannabis against the negative psychiatric effects associated with it".

"Until now, we didn't know which brain areas were responsible for this difference in effects caused by marijuana," says Professor Steven Laviolette, who conducted the study. "These findings are important because they explain why some people have a very positive experience of marijuana while others have a very negative experience," adds Christopher Norris, co-author of the paper. "Our data indicate that this is because reward and aversion are produced by anatomically distinct areas. The different effects in different individuals are probably due to genetic variations resulting in different sensitivity in each area.

This research comes at a time when France is in the midst of a debate on the legalization of cannabis for therapeutic use.

The possibility of a therapeutic hemp supply chain in the Creuse

A few months ago, the National Agency for the Safety of Medicines (ANSM) declared itself in favour of the use of cannabis for therapeutic purposes on the sole condition that it be reserved for "patients in certain clinical situations and in the event of insufficient relief or poor tolerance of accessible therapies, whether medicinal or not (and in particular specialities based on cannabis or cannabinoids available)".

In April, during a visit to Creuse, Prime Minister Edouard Philippe put the subject back on the table. "There are many countries working on this, many countries that allow it. It would be absurd not to ask the question and it is in this spirit that we want to work with the project leaders," he said, referring to the possibility of creating a "therapeutic hemp sector" led by Éric Corréia, an anaesthetist nurse trained in pain management. "It is not at all a question of endangering public health (...) We want to do things in a very controlled way," he continued.

Then, in May, a group of patients called hopeful (im)patients was formed to demand this famous legalization so that they would no longer have to buy from abroad or on the black market. The collective also asks that "the possibility of prescribing such treatments is not only the responsibility of specialised doctors in order to allow full accessibility for patients". Twenty-five associations have already planned to join the collective.