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Regular use of cannabis can cause serious cognitive impairment that persists beyond the period of being high, a speaker at next week’s cannabis and health symposium says.

University of Wollongong’s Associate Professor Nadia Solowij, who will be speaking at the New Zealand Drug Foundation’s cannabis and health symposium in Auckland, says memory, attention and higher cognitive functions were all impacted in the long-term by regular heavy cannabis use.

“The longer you use cannabis and the more heavily you use cannabis, and the younger you are when you start using cannabis, the greater the changes that we see in the actual structure of the brain,” Associate Professor Solowij said.

“The adolescent brain is more sensitive to insult from drugs, and we’ve been finding that the younger people start using, the worse the cognitive impairment.

“There are cognitive impairments that persist beyond the period of acute intoxication, and these are largely in the domains of memory, attention and higher cognitive functions.”

Associate Professor Solowij, who has been researching cannabis’ effects on the brain for over 20 years, said that her research has focussed on the relationship between cannabis use and schizophrenia and other mental health issues.

“We’re now trying to understand what is it that makes a person vulnerable to developing schizophrenia if they use cannabis.

“There are millions of cannabis users worldwide but clearly they don’t all develop schizophrenia so we’re trying to understand what makes a person vulnerable to developing schizophrenia if they use cannabis, and by what mechanisms might cannabis trigger psychosis.

“There’s really a fine line between diagnosis of schizophrenia and bipolar. They lie along the same sort of continuum of psychotic disorders. There may well be future streams of research looking more specifically at associations between cannabis use and bipolar.”

Associate Professor Solowij said she was concerned about the younger age at which people were starting to use cannabis.

“It’s one thing for adults to choose to do what they do recreationally, but with young people — where the brain is developing in really critical ways — it’s really important to try to understand what’s going on there when they use cannabis.

“Millions of them will end up not developing anything really major, but for those who do develop a psychosis it’s very tragic.

“I think it’s really important to understand why that happens to some individuals and others can go on happily smoking for many years.”

Associate Professor Solowij said that in the last 20 years a lot more evidence about the effect of cannabis on the brain had come to light.

“In the early days we used to say ‘you’ve got to be joking cannabis is a pretty mild drug’, then the evidence built and built.

“We discovered cannabis receptors and the whole endocannabinoid system in the brain, then there were the associations with schizophrenia. With the advent of neuroimaging we have whole new tools to use.”

New Zealand Drug Foundation Executive Director Ross Bell said that it was great to have Associate Professor Solowij back in New Zealand talking about the cognitive impacts of cannabis.

“In the last 20 years, a lot has changed about our understanding of the cognitive effects of cannabis and Nadia has been at the cutting edge of the research,” Mr Bell said.

“Associate Professor Solowij will help shed more light than heat on the complex issues of cognitive impairment and relationship between cannabis use and mental health issues.”

What: 2013 International Drug Policy Symposium. Through the maze: Cannabis and Health
Where: Rendezvous Hotel, 71 Mayoral Drive, Auckland
When: 27–29 November, 2013
Info: www.drugfoundation.org.nz/cannabis-and-health

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