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article imageHigh-strength marijuana is increasing cases of psychosis: study

By Marcus Hondro     Nov 29, 2015 in Science
A newly-released study from London has found high-potency marijuana is of great danger to the brain. Skunk cannabis is the name of the high potency marijuana studied — there are many others — and the results reveal it may be leading to psychosis.
Psychosis and marijuana
From the Institute of Psychiatry at King's College and entitled Proportion of patients in south London with first-episode psychosis attributable to use of high potency cannabis: a case-control study, the study found high-potency marijuana damages nerve-fibres in the brain and can break down the communication between the right and left hemispheres.
The study found a rise in psychosis amongst marijuana smokers in the South London area that has taken place can be attributed to the strong skunk cannabis. Two publications, the Daily Mail and the Guardian, after crunching numbers from the study, said the potent weed has led to a three-fold increase in cases of psychosis among 16- to 24-year-olds in South London.
The Guardian spoke with a neurobiologist and co-author of the study, Paola Dazzan, and she noted the culprit is the tetrahydrocannabinol, the THC, in pot, the ingredient that gets the user high. There are about 100 high-potency brands of pot out there that contain as much as 14 percent THC, whereas "regular" pot contains but 2-4 percent THC.
The brain and cannabis
What marijuana does, particularly high-strength marijuana, the study found, is damage an area of the brain called corpus callosum, the region with the most white matter; white matter transmits brain signals from one region of the cerebrum to another and from the cerebrum to other areas of the brain.
"If you look at the corpus callosum, what we’re seeing is a significant difference in the white matter between those who use high potency cannabis and those who never use the drug, or use the low-potency drug," Professor Dazzan said.
"What we can say is if it’s high potency, and if you smoke frequently, your brain is different from the brain of someone who smokes normal cannabis, and from someone who doesn’t smoke cannabis at all."
Studies on pot
There have been a multitude of studies of late showing marijuana usage can have grave consequences, especially for the young. Dr. Romina Mizrahi, director of the Focus on Youth Psychosis Prevention clinic at the Centre for Addiction and Mental Health (CAMH) in Toronto, who has studied marijuana, said the damage can be serious.
"Teenagers think that cannabis is harmless," she said. "It is not. And for some people, it's particularly dangerous."
A Harvard study from March said a "need for widespread education and intervention efforts among youth" exists after finding teens who smoked pot had poorer scores on tests determining brain damage.
A 2012 New Zealand study tracked over 1,000 teens from that country and found that those who used marijuana more than once per week suffered a loss of intelligence. Other studies have also found a link between pot and psychosis.
This latest study was published in the journal Lancet Psychiatry.
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