Pubdate: Tue, 07 Jan 2014
Source: Chronicle Herald (CN NS)
Copyright: 2014 The Halifax Herald Limited
Contact:  http://thechronicleherald.ca/
Details: http://www.mapinc.org/media/180
Author: Lois Legge

STUDY PROBES EFFECT OF CANNABIS ON BRAIN

Researchers Seek Reasons Drug Can Prompt Psychosis in Youth

Dr. Philip Tibbo clicks on an image of the brain and colour-coded 
white matter fills his office computer screen.

But these days he is also delving into other mysteries of the mind as 
grey as the smoke from a controversial weed.

Specifically, cannabis, a drug researchers believe can trigger 
psychosis in the still-developing brain, especially in people under 25.

And especially those who may be predisposed to schizophrenia or other 
psychotic illnesses.

That is something study after study has found, although no one knows 
exactly how it happens.

"Now, we're looking at the biology behind it," says the Halifax 
psychiatrist, professor and researcher.

Tibbo and a small team of researchers are looking inside young brains 
to see how cannabis disrupts the circuitry, hampers the vital 
connections needed to think, reason and remember clearly.

The study is unique, he says, because it is using three MRI-based 
neuroimaging techniques he hopes will provide a clear map of what 
cannabis does to the white matter, neurochemicals and micro structure 
of the still-forming brain.

It includes about 180 participants, divided into two main groups: a 
healthy control group and a patient group.

Each will include people who have used cannabis before age 17, 
started using it later or never used it.

Tibbo heads the Nova Scotia Early Psychosis Program, and his own 
studies and clinical experience already point to a clear link between 
cannabis use in young people and diagnoses of schizophrenia or other 
psychotic disorders.

Research also shows it can worsen symptoms, usually delusions and 
hallucinations.

Psychosis typically develops from ages 18 to 25, often the primary 
period - or even earlier - people smoke pot, Tibbo says.

It's also a time when the brain's frontal lobe is still developing.

"So what the research has shown is within that period if there's 
cannabis use, it can disrupt that process."

That is especially true in those already predisposed to psychosis, 
perhaps even triggering its onset, says the Dr. Paul Janssen Chair in 
Psychotic Disorders at Dalhousie University.

"You will increase your risk for psychosis by about four times. You 
look at a lot of the larger epidemiological studies and they can back that up."

His centre helped develop a national study by Schizophrenia Society 
of Canada - Cannabis and Psychosis: Exploring the Link 
(www.cannabisandpsychosis.ca) that found more evidence of a strong connection.

It trained 28 young people with psychosis to become research 
assistants in three Canadian centres: Halifax, London and Vancouver.

They helped recruit other young people for one-on-one interviews or 
focus groups exploring their experiences with the drug.

"We were trying to figure out why (they were) smoking and how did 
they feel that cannabis related to their illness," Tibbo says.

"And most of them did say that, yes, they felt that (cannabis), if 
not precipitated their illness, made their symptoms worse and 
affected their recovery. Definitely they see that link."

He says he stays away from the politics of the drug, which has been 
approved for some medical purposes.

But Tibbo wants young people to know about its risks.

"Even in the studies with cannabis in a regular population, we can 
show that it affects how you think and your cognition in the long 
term. So add psychosis on top of that (and) it's another hit on the brain.

"As a doctor, we're trying to make sure everybody's as healthy as we 
possibly can and we know that cannabis itself can just derail everything."
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MAP posted-by: Jay Bergstrom