In a study published in the journal Jama Network Open, Canadian researchers are concerned about the explosion of new cases of schizophrenia in their country, triggered by the use of cannabis. The figure would have tripled since 2015, when this drug was legalized in Canada. Schizophrenia is a psychic disease that results in a disturbed perception of reality, delusional ideas or hallucinations, and in social and relational isolation. Symptoms (nature and severity) are different from one person to another.
Aggravated symptoms with cannabis
In less than 20 years, the number of people who have been diagnosed with schizophrenics because of their cannabis consumption has increased from 4 to 10%, reveal the researchers. The latter also point out that the use of this drug aggravates the symptoms of the disease. “”Regular consumption of cannabis is strongly associated with an increase in the risk of schizophrenia “, said Dr. Daniel Myran, expert in public health and preventive medicine at the University of Ottawa, and co-author of the study. For the doctor, this case explosion “underlines the urgent need for targeted prevention strategies, in particular for younger populations who seem to be the most exposed to this risk ”.
Many young men admitted to emergencies
In France, the consumption of cannabis for recreational use is prohibited. The use of cannabis in a medical framework (therapeutic cannabis) was experienced from March 2021 to December 2024. But to ensure the continuity of the management of patients treated during experimentation and always under treatment, a transition period was initiated. It will end on March 31, 2026.
In Canada, therapeutic cannabis was legalized in 2015 and cannabis for recreational use was legalized in 2018.
The study led by Dr. Myran was interested in the number of citizens living in southern Canada, aged 14 to 64, having been admitted to emergencies between 2006 and 2022. During these 17 years, 80s 523 people were admitted to the emergency room for a schizophrenic disorder. Among them, 10,583 had said regularly consuming cannabis, including many young men.
But that’s not all, the researchers found that the number of patients requiring hospital care to treat their cannabis addiction had increased by 270% since the legalization of the recreational use of cannabis. Over the same period, the percentage of new cases of schizophrenia requiring hospitalization (before the diagnosis of the disease is made) increased from 7 to 16%.
What is the link between use of cannabis and schizophrenia?
Most cannabis consumers will not develop schizophrenia. However, in people with fragile mental health (suffering from mood disorders or anxiety disorders for example), smoking cannabis could promote the occurrence of schizophrenia.
The risk would increase with the quantities consumed. The more you smoke, the more risk of developing the disease. As a result, the risk would be multiplied by 4 for a regular consumer. Note that the use of cannabis before the age of 15, while the brain has not reached its maturity, would be an additional risk factor.