Daily Use Of ‘High Grade’ Marijuana Is Linked To Psychosis, Study Finds

A new study commissioned by professionals in Europe found that daily use of the drug marijuana, especially high strains, is linked to an increased risk of the development of psychosis.

The study, published on Tuesday, looked at cannabis use in 11 major cities and Brazil, and is the first to show the impact of marijuana use on rates of psychosis, a severe mental condition, in large populations. According to the study, the link with psychosis was strongest in London and Amsterdam where strains of marijuana containing over 10 percent THC, the psychoactive component of the drug, are highest and most commonly available.

Dr. Marta Di Forti, the lead author from the Institute of Psychiatry, Psychology, and Neuroscience at King’s College, in London, told NBC News that the findings were in line with previous studies concluding that use of the drug with high levels of THC is more harmful than weaker strains.

“Our findings are consistent with previous studies showing that the use of cannabis with a high concentration of THC, also known as skunk-like cannabis, has more harmful effects on mental health than weaker forms,” Mr. Di Forti said. “For the first time we have consistent evidence that there is a dose-dependent relationship between cannabis use and induced psychosis at a population level. The more cannabis you consume the more likely you are to develop a psychotic disorder.”

According to NBC, the strains were classified as either high potency — over 10 percent THC — or low potency — under 10 percent THC.

The study found that people who used any type of cannabis on a daily basis were three times more likely to have a diagnosis of a new episode of psychosis, compared with people who had never used cannabis. This increased to five times more likely for daily use of high potency cannabis.

Of all new cases of psychosis across the 12 sites during that time period, an estimated one in five new cases of psychosis were linked to daily cannabis use. One in 10 were linked to use of high potency cannabis, the study found.

“THC is the culprit in the psychotic events,” Mr. Di Forti.

In the Netherlands, the THC content reaches up to 67 percent in certain cities such as Nederhasj. In London, skunk-like cannabis, known for its strong stench, represents 94 percent of the street market and has an average THC of 14 percent, according to NBC.

Previous research has linked .marijuana use and psychosis, but those studies were not performed in large enough populations to provide reliable results.

A Canadian study published in the Journal of Child Psychology and Psychiatry in 2017 showed a substantial increase in “psychotic-like experiences” in teenage users. The study also reported adverse effects on cognitive development and increased symptoms of depression.

The U.S. Virgin Islands has legalized marijuana for medical use, but former Senator and Dept. of Agriculture Commissioner Nominee Positive Nelson, who led the effort, said his ultimate goal is to see the drug legalized for recreational use in the territory. Mr. Nelson is hosting an event at the University of the Virgin Islands’ Great Hall on Friday afternoon, called “Let’s Talk Cannabis”, where he is expected to present on the recently passed law and regulations of the drug in the territory.