High potency pot 'strongly linked' to psychosis: study

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High potency cannabis, especially when used daily, is "strongly linked" to the risk of developing psychotic disorders such as schizophrenia and paranoia, scientists said Wednesday.

In Amsterdam and London—where high-THC marijuana has long been the rule rather than the exception—50 and 30 percent of new psychosis cases, respectively, were associated with potent forms of the drug.

The findings, reported The Lancet, bolster a growing body of research connecting pot to a range of disorders.

With piecemeal legalisation and decriminalisation, consumption in North America and Europe has increased markedly over the last two decades, even as levels of the drug's mind-bending molecule, delta-9-tetrahydrocannabinol (THC), have risen four- or five-fold.

"The use of cannabis with a high concentration of THC has more on mental health than the use of weaker forms," said lead author Marta Di Forti, a professor at the Institute of Psychiatry, Psychology and Neuroscience at King's College London.

"Our findings also indicate for the first time how affects the incidence of psychotic disorder at a population level."

Across 11 European cities or regions, and a 12th in Brazil, one in five new cases of psychosis were associated to daily cannabis use, and one in ten to high potency pot, the study found.

Trainwreck, gorilla glue

If high-THC cannabis—including strains such as "trainwreck", "gorilla glue", and "hindu kush"—were no longer available, "12 percent of cases of first-episode psychosis could be prevented across Europe," the researchers calculated.

In Amsterdam, the incidence of first-time psychosis would likely drop from 38 to 19 per 100,000 people per year, while in London, the number of cases would decline from 46 to 32 per 100,000 people.

"As the legal status of cannabis changes in many countries and states, and as we consider the medicinal properties of some types of cannabis, it is of vital public health importance to consider the potential adverse effects that are associated with daily cannabis use, especially high potency varieties," said Di Forti.

The researchers established a baseline by identifying—in the cities and regions examined—all individuals known to have experienced a first episode of psychosis from 2010 to 2015. They found 901 cases.

These were then compared to 1,237 healthy adults to tease out the risk factors associated with psychosis.

All participants provided information about how frequently they had used marijuana and other drugs over a period of years. The scientists also classified the potency of the cannabis consumed as either "high" (over 10 percent THC) or "low" (under 10 percent THC).

In some locations, THC levels are 20 percent or higher, they noted.

Nearly 30 percent of patients who had experienced a first episode of psychosis were daily cannabis users, compared with less than seven percent of those in the control group.

For high potency pot, the corresponding figures were 37 and 19 percent.

Adjusting for social factors and other drug use, the authors found that daily cannabis users were three times more likely to experience psychosis for the first time than people who had never used it.

For daily use of high-potency cannabis, this increased to five times.

While the correlation between marijuana use and mental disorders was strong, a cause-and-effect relationship can only be inferred, the authors cautioned.

However the registrar at the Royal College of Psychiatrists, Adrian James, said the findings were to be "taken seriously," and that his institution "is reviewing the mental health effect of cannabis use."

David Nutt, head of the centre for neuropsychopharmacology at Imperial College London, said it was "important to realise that THC is well known to produce psychosis in healthy volunteers—people without a predisposition to mental illness".


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Psychosis five times more likely for cannabis users, study finds

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Mar 20, 2019
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Mar 20, 2019
How much is big Pharma paying for these bogus studies?

Mar 20, 2019
It's not psychosis, it's called being high. Smoke a little less next time.

Mar 20, 2019
I think it's safe to say the majority of us who have smoked for 30 - 50 years are tired of the Internet's ability to confuse and dumb-down the uninformed public at the stroke of yet another anti-marijuana "study". Studies, as we should all know by now, are largely bought-and-paid-for annoyances. Studies, thus far, which can offer no bona fide examples of medical/psychological verified proof.

The overabundance of stats and pretty graphs are pure bullshittery of the highest degree.
By the way, perhaps you should have included the 1936 propaganda film "reefer Madness" in your references?

Mar 20, 2019
This comment has been removed by a moderator.

Mar 20, 2019
The flood of comments to these kind of stories is always SO predictable.

Anyone, and everyone, who is the least familiar with Pot Culture has heard about paranoia or wigging / freaking out. Everyone. I know users stopping after such experiences- as have celebs (ie Howard Stern).

Is it really any surprise that the relatively _small_ percentage of the population genetically prone to paranoid psychosis should probably avoid using pot (or, at the very least, the industrialized, high-THC content variety)?

But Noooooo! It's always "God / Jah's Perfect Gift" or "Mother Nature's Solution to Everything." And any dissent to that Dogma has been part of a massive Reefer Madness PLOT from the Liquor Industry, Big Pharma, Anti-Mexican Racists and (my favorite!) "The Wood Paper Pulp Industry Colluding with Hearst Newspapers!" (tho, I must admit, throwing the Illuminati into the mix is a new twist! A+ for hazy creativity there, sport! )

Pssssfffttt....hey duddddddde....paranoid much?

Mar 20, 2019
Predictably, whenever you present a personal,or anecdotal, story about the negative aspects of chronic pot use, you can expect the usual reply - "THEY are the problem, not "US." This is exactly the same reply given to any challenger of any authoritarian religion or government.

We already control, regulate and standardize the potency of OTC medicines and alcohol - not to mention mandating Warning Labels. The Pot Industry should expect the same.

Mar 20, 2019
The legal pot industry brought this mess on themselves, by letting stoners define the product based on mind blowing instead of mellowness. I know old hippies in CO who won't touch the legal stuff, because it's too strong. People want the equivalent of a beer or glass of wine, and the companies are pushing the equivalent of syringes of pure ethanol. Wanting to mellow out is one thing, but wanting to escape reality is always pathological, always a road to madness with alchohol or any drug. So why is the product geared to going nuts instead of occasional use by people with no tolerance built up?

Mar 20, 2019
"It's not psychosis, it's called being high. Smoke a little less next time."
Being high as space may leave you crashed on the ground or literally crash your mind in a way you won't like to try it again. And it doesn't help legalization efforts.
I believe nowadays it is much easier to get bad trip and psychosis from high potency pot than from psychedelics like mushrooms. It's bad not only because the THC content is so high, but also because it's not well-balanced by other cannabinoids that have modulating effects on its potency, decreasing psychosis risk. It's not even clearly verified how specific cannabinoids in mixes actually affect neuronal signalling and states of mind. But of course you have to know something aout it 'cause everyone knows different varieties of cannabis bring completely different high depending on the active contents balances. Nowadays trying to find nice pot is like going out for one beer only to find shops selling exclusively absolute alcohol.

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