Schizophrenia linked to marijuana use disorders on the rise, study finds

(CNN) – The proportion of schizophrenia cases linked to problematic marijuana use has increased over the past 25 years, according to a new Danish study.

In 1995, 2% of schizophrenia diagnoses in the country were associated with a cannabis use disorder. In 2000, it rose to around 4%. Since 2010, this figure has risen to 8%, according to the study.

“I think it is very important to use both our study and other studies to underline and stress that cannabis use is not harmless,” said Carsten Hjorthøj, associate professor at the Research Center of Copenhagen for Mental Health and author of the study published in the medical journal JAMA Psychiatry, by email.

“There is, unfortunately, evidence to suggest that cannabis is increasingly viewed as a somewhat harmless substance. This is unfortunate because we see links to schizophrenia, lower cognitive function, substance use disorders, etc. Hjorthøj wrote.

Previous research has suggested that the risk of schizophrenia is increased for people who use cannabis, and the association is particularly driven by heavy use of the drug. Many researchers hypothesize that cannabis use may be a “component cause”, which interacts with other risk factors, to cause disease.

“Of course, our results will have to be replicated elsewhere before any firm conclusions can be drawn,” continued Hjorthøj. “But I’m pretty confident that we’ll see similar patterns in places where problematic cannabis use has increased, or where potency of cannabis has increased, as numerous studies suggest that high potency cannabis is likely driving it. ‘association with schizophrenia. “

Around the world, tens of millions of people use cannabis. It is legal for recreational use in 19 US states and Canadian. In these and other places, it is also approved to treat certain medical conditions.

Cannabis use and cannabis use disorders on the rise in Denmark, study finds – a model that is also seen globally. Recreational use of weeds is illegal in Denmark but is permitted for medicinal purposes.

Cannabis use disorder is generally defined as problem drug use: developing tolerance to the herb consuming cannabis in greater amounts or over a longer period of time than expected; being unable to reduce use; spending a lot of time obtaining, using or recovering from the effects of cannabis; renounce important activities and obligations in favor of cannabis; and continued drug use despite negative consequences.

An increase in schizophrenia?

Schizophrenia is a chronic, serious and disabling mental disorder. Its symptoms may include delusions, disturbed thinking and hallucinations. Global, Schizophrenia affects 20 million people. No cure exists, so doctors try to manage the symptoms with medication and therapy.

While one study has suggested schizophrenia is on the rise in Denmark, in other countries the picture is uncertain, Hjorthøj said. In the United States, the National Institute of Mental Health said precise estimates of the prevalence of schizophrenia are difficult to obtain because the diagnosis is complex and overlaps with other disorders.

“Many psychiatric textbooks assert that the incidence … of schizophrenia is constant over time and independent of geographic location,” Hjorthøj said.

“And this has often been used as an argument against the hypothesis that cannabis could cause schizophrenia,” he added. “However, it turns out that there is very little research that would support this notion.”

The new study was based on data from the Danish National Health Register and included all people in Denmark born before December 31, 2000, who were 16 years of age or older at some point from January 1, 1972 to December 31, 2016.

The findings could help explain “the general increase in the incidence of schizophrenia that has been observed in recent years” and support that “the long-observed association between cannabis and schizophrenia is likely partially causal in nature”, according to the study.

Legalization and regulation

The study evaluated people who had a clinical diagnosis of cannabis treatment disorder, not general drug use, noted Terrie Moffitt, professor and chair of social behavior and development at the Institute of Psychiatry, of. psychology and neuroscience from King’s College London.

“This nationwide medical records study adds important evidence that patients with diagnosed cannabis use disorder are at greater risk for psychosis today than they were previously,” Moffitt said , who studies the effects of cannabis use on the mental health of the baby boomer generation, told the Science Media Center in London.

However, Moffitt said most cannabis users, even those who depend on it, never seek treatment, and many people use it recreationally without developing problems.

“We know that people who seek treatment tend to have multiple mental health issues, not just cannabis issues,” Moffitt said. “And there are many more recreational cannabis users who manage cannabis well than addicted cannabis users who cannot.”

In an editorial that accompanied the study, Tyler J. VanderWeele, a professor in the departments of epidemiology and biostatistics at the Harvard TH Chan School of Public Health, said the study’s estimates may be conservative due to the under- diagnosis of cannabis use disorders.

“Cannabis use disorder is not responsible for most cases of schizophrenia, but it is responsible for a significant and growing proportion. This should be taken into account in discussions regarding the legalization and regulation of cannabis use, ”VanderWeele wrote in the commentary.

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