Smoking marijuana increases the likelihood of developing schizophrenia. Teenage boys and young men are especially vulnerable

Marijuana use can lead to mental disorders. Photo: vecteezy.com

Schizophrenia is a complex pathology. It is characterized by disturbances in thinking, perception, and behavior. Schizophrenia varies greatly from person to person. It can manifest with various symptoms, including hallucinations, delusional ideas, speech impairment, and social maladjustment. People suffering from schizophrenia may experience impaired memory, attention, and motivation, as well as problems with communication and functioning in daily life. The disease affects approximately 1% of the population.

A new study by the Danish Mental Health Service and the American National Institute on Drug Abuse, the results of which were published in the journal Psychological Medicine, demonstrates that excessive use of cannabis products increases the risk of developing schizophrenia, especially in young men.

Scientists conducted a nationwide registry-based cohort study including all residents of Denmark aged 16 to 49 years for the period from 1972 to 2021. As a result, data on over 6.9 million people were examined. Of these, more than 45 thousand suffered from schizophrenia.

According to the researchers, preventing marijuana use could reduce the number of schizophrenia cases by 4% among women and 15% among men aged 16 to 49. Furthermore, a 30% reduction in incidence could occur in the age group of men aged 21 to 30.

Of particular concern is the increase in THC (tetrahydrocannabinol) content in products available on the market. For example, its content increased from 13% in 2006 to 30% in 2016.

Psychiatrist Jean-Michel Delile, president of the "Fédération Addiction", quoted by the French publication Le Monde, notes:

"The Danish study is robust because it was conducted by a very strong team. It shows that young men are the most vulnerable. This confirms other studies that have demonstrated a very strong correlation between marijuana use and the presence of mental disorders."

For example, a Swedish study of 45,000 conscripts, published in The Lancet in 1987, showed that the more young people used marijuana before joining the army, the greater their risk of developing a mental disorder.

Similarly, a study conducted in New Zealand in 2002 showed that individuals who started using marijuana before the age of 15 and continued to use it in relatively large quantities were at a significantly higher risk of developing mental disorders.

It increased three-fold for regular users and ten-fold for those who started using marijuana before the age of 15.

Le Monde quotes child psychiatrist and head of the research group at the French National Institute of Health and Medical Research (INSERM), Jean-Luc Martinot, who notes that

"the Danish study shows that for boys, the age of 13 to 16 is the most vulnerable. Brain maturation in boys occurs later than in girls, in terms of gray matter structure and white matter microstructure."

During adolescence, the circuits of the prefrontal cortex, which are involved in complex cognitive processes, language, and reasoning, undergo significant changes; the brain is extremely plastic, and its development rate is substantial.

As is known, THC from marijuana affects cannabinoid receptors, which play an important role in brain development. This active component acts on brain areas associated with psychiatric disorders, especially in areas where brain plasticity is most pronounced during adolescence.

As Jean-Luc Martinot notes, marijuana can alter some important brain circuits responsible for cognitive functions, thinking, and emotion regulation. This affects academic performance, relationships with other people, and leads to anxiety disorders.

With regular consumption, marijuana becomes a factor that increases isolation and alienation from the surrounding world.

Le Monde quotes another member of the INSERM research group, psychiatrist Marie-Odile Krebs, who notes:

"Marijuana is one of the most important risk factors for the development of schizophrenic disorder; other factors include genetic or family predisposition, and the presence of attenuated symptoms."

Attenuated symptoms (also known as prodromal or problematic symptoms) refer to the precursors or early manifestations of a mental disorder, such as schizophrenia. These symptoms may be less pronounced or non-specific, making them difficult to diagnose. Attenuated symptoms can include changes in thinking, emotions, or behavior that may be unusual or deviate from typical patterns. Some such symptoms include changes in interpersonal relationships, poor concentration, social withdrawal, lack of motivation, or communication difficulties. Understanding attenuated symptoms can aid in early detection and treatment of mental disorders.

She draws a parallel between tobacco smoking addiction and lung cancer.

Child psychiatrist Jean-Luc Martinot insists on expanding preventive measures, taking into account the physiological period of development, especially in adolescent boys, and individual developmental factors. In his opinion, "universal preventive messages do not work well."

Le Monde quotes Jean-Michel Delile, author of another study published in the journal Psychotropes in 2022, who notes that it is marijuana use that precedes the appearance of mental disorders, and not vice versa. According to the scientist,

"at a time when there is a movement towards the decriminalization of marijuana, one should not underestimate the harm associated with its use by young people, especially adolescents."

Read more:

How marijuana is linked to surgery — what doctors have learned

A European country for the first time completely legalizes marijuana

Scientists: Marijuana destroys the brain

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