In young men, study finds 15% of schizophrenia may be preventable in absence of cannabis use disorder

A large study of 6.9 million Danish health records over 50 years found “strong evidence” of an association: Cannabis Use Disorder (CUD) and schizophrenia, both men and women. The magnitude of this relationship is consistently greater for men than women, and much greater for younger men, especially those aged 16 to 25, the researchers said.

Using statistical methods based on Danish National Health Record data, the researchers found that at least 15% of male schizophrenia cases would be “preventable” by 2021 if cannabis use disorders were not present. It’s possible,” he said, “conservatively.” For women, the equivalent figure is her 4%.

There is also a widespread impression that cannabis use is “harmless”, as attitudes toward cannabis use are generally more tolerant, especially in Western countries, including the United States, Canada and Europe, due to the steady legalization process over the past decade. increase. researchers point out.

They do not agree with this, repeating the warnings that have been repeatedly voiced in recent years. Dr. Nora Volkow, a member of the BBRF’s Scientific Council and director of the U.S. National Institute on Drug Abuse. Dr. Volkow was a member of the team that conducted the Danish study. psychiatry.

Noting specifically the contribution of schizophrenia and frequent and regular cannabis use consistent with the increasing incidence of schizophrenia over the past few decades, the researchers wrote: many Cases of schizophrenia in Denmark [the nation whose population served as the basis for the new research]the CUD is expected to increase steadily to a non-negligible degree. ratio” Number of people with schizophrenia in the last 50 years.

Among young men aged 21 to 30 and possibly up to 40, the percentage of schizophrenia cases that could be avoided in the absence of CUD “could be as high as 25 to 30%,” the researchers noted. ing. For this reason, the researchers said they believe CUD is “a major modifiable risk factor for schizophrenia, especially in men.”

The reasons for this remarkable statistic are not clearly known, but researchers have noted an increase in cannabis use in the general population and a concomitant increase in the efficacy of cannabis products (based on the concentration of the active ingredient, THC). We propose that the increase likely helps explain the study results. A steadily increasing proportion of new cases of schizophrenia may be preventable without heavy and regular cannabis use, especially by young male users.

Led by Dr. Carsten Hjortozzi, an epidemiologist at the Danish Capital Territory Mental Health Service and the University of Copenhagen, the research team included collaborators from the US National Institutes of Health, including Dr. The medical database consists of all people in Denmark between the ages of 16 and 49 at any point in time between 1972 and 2021. This included more than 6.9 million health records for him, of which 51% were men. Of these, a total of 45,327 were diagnosed with schizophrenia at some point during his 50-year study. During the same period, 60,563 people were diagnosed with a cannabis use disorder, three-quarters of whom were men.

Such an extensive study, in this case using over 129 million person-years of comprehensive medical follow-up data, produces statistical data with a very low potential error rate. A major limitation is that diseases such as schizophrenia and CUD only “appear” in Danish national records if they are actually diagnosed and entered by a medical professional. There have been a few cases of people who had both conditions but were not diagnosed. Therefore, the statistical results of this study are down-trend and ‘conservative’. The research results are relevant. Causality of cannabis use disorders in the development of schizophrenia cannot be proven.

“We cannot be certain of the percentage, but [cannabis]- In exposed individuals who may have developed schizophrenia in the absence of CUD, it is unlikely that all symptoms will lead to schizophrenia. [observed] The link between CUD and schizophrenia may be explained by confusing facts,” they noted.

Cannabis use disorder is defined by a persistent desire or unsuccessful effort to reduce or control cannabis use. Much time is spent on the activities necessary to obtain cannabis, use cannabis, or recover from its effects. There is usually a strong desire or urge to use cannabis.

The researchers say more research is needed into the association between cannabis use frequency and THC levels in both men and women and schizophrenia, and potential causal relationships. But they are clear in their conclusion. While noting “significant differences between men and women in the acute and long-term effects of cannabis,” they said the results “suggest a relationship between intensive cannabis use and the risk of developing schizophrenia.” increase. ”, at the level of the population as a whole. At the individual cannabis user level, “the risk occurs in both men and women, but is higher among young men.”

The researchers believe that the increasing proportion of schizophrenia cases could be avoided by preventing CUD. They say their findings encourage health care providers to effectively screen for and treat cannabis use disorders in general and in young men who may be using cannabis on a regular basis, in particular. He said he hopes that They appear to be the most vulnerable to the as yet unexplained effects of cannabis, especially highly potent and regularly used cannabis, on the development of psychotic disorders.

“The entanglement of substance use disorders and mental illness is a major public health problem that requires an urgent response and support for those who need it,” Dr. Bolkow noted. “As access to potent cannabis products continues to expand, it is also important to expand prevention, screening and treatment for those who may experience mental illness related to cannabis use. It’s a step in the direction and will help inform not only the decisions individuals make about their own cannabis use, but also the decisions healthcare providers may make in caring for their patients.”