Link between pot, psychosis goes both ways in kids

NEW YORK Tue Dec 25, 2012 4:57pm EST

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NEW YORK (Reuters Health) - Marijuana (cannabis) use may be linked to the development of psychotic symptoms in teens - but the reverse could also be true: psychosis in adolescents may be linked to later pot use, according to a new Dutch study.

"We have focused mainly on temporal order; is it the chicken or the egg? As the study shows, it is a bidirectional relationship," wrote the study's lead author Merel Griffith-Lendering, a doctoral candidate at Leiden University in The Netherlands, in an email to Reuters Health.

Previous research established links between marijuana and psychosis, but scientists questioned whether pot use increased the risk of mental illness, or whether people were using pot to ease their psychotic symptoms, such as hallucinations and delusions.

"What is interesting in this study is that both processes are going on at the same time," said Dr. Gregory Seeger, medical director for addiction services at Rochester General Hospital in upstate New York.

He told Reuters Health that researchers have been especially concerned about what tetrahydrocannabinol (THC), the active property in pot, could do to a teenager's growing brain.

"That's a very vulnerable period of time for brain development," and individuals with a family history of schizophrenia and psychosis seem to be more sensitive to the toxic effects of THC, he said.

A 2010 study of 3,800 Australian teenagers found that those who used marijuana were twice as likely to develop psychosis compared to teens who never smoked pot (see Reuters Health article of March 1, 2010 here:).

But that study also found that those who suffered from hallucinations and delusions when they were younger were also more likely to use pot early on.


For the new study, published in the journal Addiction, the researchers wanted to see which came first: pot or psychosis.

Griffith-Lendering and her colleagues used information on 2,120 Dutch teenagers, who were surveyed about their pot use when they were about 14, 16 and 19 years old.

The teens also took psychosis vulnerability tests that asked - among other things - about their ability to concentrate, their feelings of loneliness and whether they see things other people don't.

Overall, the researchers found 940 teens, or about 44 percent, reported smoking pot, and there was a bidirectional link between pot use and psychosis.

For example, using pot at 16 years old was linked to psychotic symptoms three years later, and psychotic symptoms at age 16 were linked to pot use at age 19.

This was true even when the researchers accounted for mental illness in the kids' families, alcohol use and tobacco use.

Griffith-Lendering said she could not say how much more likely young pot users were to exhibit psychotic symptoms later on.

Also, the new study cannot prove one causes the other. Genetics may also explain the link between pot use and psychosis, said Griffith-Lendering.

"We can say for some people that cannabis comes first and psychosis comes second, but for some people they have some (undiagnosed) psychosis (and) perhaps cannabis makes them feel better," said Dr. Marta Di Forti, of King's College, London, who was not involved with the new research.

Di Forti, who has studied the link between pot and psychosis, told Reuters Health she considers pot a risk factor for psychosis - not a cause.

Seeger, who was also not involved with the new study, said that there needs to be more public awareness of the connection.

"I think the marijuana is not a harmless substance. Especially for teenagers, there should be more of a public health message out there that marijuana has a public health risk," he said.

Griffith-Lendering agrees.

"Given the severity and impact of psychotic disorders, prevention programs should take this information into consideration," she said.

SOURCE: Addiction, online December 7, 2012.

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Comments (38)
mitzimatters wrote:
If this were true millions and millions of people would suffer from psychosis.
these people could have suffered from mental illness before they started smoking. I watch tv. If I go blind can I blame the TV?

Dec 25, 2012 9:16pm EST  --  Report as abuse
romikk32 wrote:
Saddest thing I EVER saw…trying to piggy back their *drug war rhetoric* on the tragedy of the Newtown shooting. What they AREN’T telling you is that this kid probably was a science experiment from the legal pharmaceutical nightmare imposed on kids today by the corporate pharma industry. Don’t drink the koolaid kids, the pharma and DEA nazis are paying BIG bucks for ANY sort of propaganda to legitimize their $$$ cash cow. even using a tragedy like Newtown.

Dec 25, 2012 9:57pm EST  --  Report as abuse
Moooose31 wrote:
What about the hundred deaths per day from prescription pill overdoses? Marijuana causes no deaths, or any of the more damaging psychotic and physical effects capable from opiate derived, and amphetamine based prescription pills. As a young person (20) I remember how easy it was for kids in school to get ADHD medicine, illegally. Often times the kids selling it would simply not take their prescription, and sell it, since it tended to drastically alter their personality. Smoking weed, versus taking ADHD medicine, from my observations, tended to calm the person down over the long term, even after periodical, moderate use. More important than psychosis, Marijauana use (not the atmosphere created by its illegality) causes no documented deaths, while cigarettes, tobacco and prescription pill deaths are an epidemic.

Dec 25, 2012 10:03pm EST  --  Report as abuse
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