Does Marijuana Use Cause Schizophrenia?

Nearly a century after the movie Folie Reefer In the United States, some politicians and doctors are once again worried about the dangers of marijuana, even though the containers have been gone for a long time.

Experts now distinguish between "new cannabis" – legal, very powerful, available in tablets, edibles and vapes – and the older version, a much softer herb that circulates in the joints. Concentrations of THC, a chemical that produces a lot of marijuana, have been increasing for at least three decades and it is now possible in some states to buy vape cartridges containing only the active ingredient.

Much of the concern is centered on the link between intensive use and psychosis in young people. Doctors suspected for the first time the existence of a link of this type 70 years ago, and the evidence has only accumulated since. In an upcoming book, Tell your children, Alex Berenson, a former New York Times According to one journalist, legalization puts a higher-risk generation of schizophrenia and other psychotic syndromes. Critics, including leading researchers, have described the argument as exaggerated and unfaithful to science.

Can cannabis use cause psychosis?

Yes, but it can be abused by caffeine, nicotine, alcohol, stimulants and hallucinogens. Psychosis is a symptom: a temporary disorientation that resembles a waking dream, with strange and imaginary images and sounds, often accompanied by paranoia or a disturbing sensation. The vast majority of people with this type of psychotic experience do not develop schizophrenia, which is characterized by recurring episodes of psychosis for years, as well as by cognitive problems and social withdrawal.

– Can intensive use cause schizophrenia or other syndromes?

This is the big question and so far the evidence is not strong enough to answer in one way or another. Even the best scientists specializing in marijuana research are divided in two, drawing opposite conclusions from the same data.

"I've been doing this research for 25 years and that even polarizes academics," said Margaret Haney, a professor of neurobiology at Columbia University Medical Center.

The debate is about the distinction between correlation and causality. People with psychotic problems often consume cannabis regularly; It is a strong correlation, supported by many studies. But it is unclear who came first, the usual cannabis or psychoses. Children who develop schizophrenia later often seem to fall back into their own world, periodically followed by bizarre fears and fantasies, far beyond the imaginary possibilities of childhood and well before being exposed to cannabis. Those who become regular users of marijuana often consume other substances, including alcohol and cigarettes, which complicates the task of researchers.

Consider cigarettes, which change the least mind of these substances. In a 2015 study, a team led by Dr. Kenneth S. Kendler of Virginia Commonwealth University badyzed the medical data of nearly 2 million people in Sweden. The data followed individuals over time, from early adulthood, to the time when most diagnoses of schizophrenia take place, up to the average age. Smoking was a predictor of the subsequent development of the disorder, and what doctors call a dose-response relationship: the more a person smoked, the higher the risk.

However, nicotine does not cause concern for cannabis, partly because of the effects so different from the two drugs in everyday life: a slight stimulation and a boil. Indeed, some scientists have studied nicotine as a partial treatment for schizophrenia, to alleviate the effects of disorders on thinking and memory.

– Is It biologically plausible that cannabis could cause a psychotic disorder?

Yes. Brain scientists know very little about the underlying biology of psychotic conditions, aside from the fact that hundreds of common genetic variants are probably involved. Schizophrenia, for example, is not a uniform disorder, but a generic term for a set of unexplained problems involving recurrent psychosis and other common symptoms.

Even in this case, there is indirect evidence of a biological mechanism. Psychotic disorders tend to occur in late adolescence or early adulthood, during or after a period of rapid brain development. In adolescence, the brain removes unnecessary or redundant connections between brain cells, according to a process called synaptic pruning. This edition is concentrated in the prefrontal cortex, the region behind the forehead where reflection and planning take place, as well as in the region disturbed by psychotic conditions.

The region is rich in CB1 receptors, involved in size and related to cannabis use. And changes in the pruning process may well increase the risk of schizophrenia, according to recent research conducted at the Broad Institute of MIT and Harvard. In a 2016 badysis, scientists found that people with this disorder often have a variant of the gene that seems to speed up the size process.

– What reDoes this mean for me?

Experts can debate whether cannabis use can lead to psychotic disorders, but they usually agree on how to minimize risk.

Psychotic conditions tend to reign in families, suggesting hereditary genetic vulnerability. According to some studies, people at risk of psychosis or at a higher risk of psychosis seem to feel the effects of cannabis differently from their peers. Users experience a brighter effect, but they are also more likely to experience psychotic effects, such as paranoia.

Evidence to date indicates that the family risk of psychotic disorders is greater than any additional effect of cannabis use. In a 2014 study, a team led by Ashley C. Proal and Dr. Lynn E. DeLisi of Harvard Medical School recruited cannabis users with and without a family history of schizophrenia, as well as non-users with and without such antecedents. The researchers ensured that cannabis users did not use other drugs in addition, which confused earlier studies. As a result, the risk of schizophrenia was increased among those with a family history, regardless of cannabis use.

"My study clearly shows that cannabis does not cause schizophrenia per se," said DeLisi. "A genetic predisposition is necessary. According to the results of this study and others, it is highly likely that cannabis use during adolescence until the age of 25, when the brain matures and reaches its peak of growth in a genetically vulnerable individual, may be at the origin of the onset of schizophrenia. "

Because marijuana has been illegal for so long, research that could resolve this issue is sorely lacking, although it has begun to change. The National Institutes of Health have launched a $ 300 million project that will track thousands of children ages 9 or 10 through to adolescence and could help clarify causation.

In the near future, the opinions of the experts will probably be mixed. "Usually, it's the researchers who make" the sky is falling apart, "but here it's switched," said Dr. Jay Geidd, a professor of psychiatry at the University of California at San Diego. "Researchers are wary of risks, as they have been in the past. However, many clinicians want to see many more adolescents with "paranoia".

In short: Consuming new high-potency cannabis regularly can be a risk for young people who are related to someone with psychosis. On this warning, at least, most experts seem to agree.