Pubdate: Fri, 29 Nov 2013
Source: Southland Times (New Zealand)
Copyright: 2013 Southland Times Company Ltd.
Contact:  http://www.southlandtimes.co.nz/
Details: http://www.mapinc.org/media/1041

PSYCHOSIS RISK HIGH IN YOUNG CANNABIS USERS

Some heavy cannabis users are up to 11 times more likely to develop 
schizophrenia, a drug symposium in Auckland has been told.

People with a certain gene combination that exists in 25 per cent of 
the population had that heightened risk, Otago University's Professor 
Richie Poulton told the Cannabis and Health Symposium.

Risk of psychosis was elevated for those who used the drug when they 
were young, the Dunedin Longitudinal Study showed, but not at the 
levels of that gene combination.

For people who used cannabis heavily before the age of 18, the risk 
of schizophrenia increased by 10.3 per cent, Prof Poulton said.

For those who used it heavily after the age of 18, the risk increased 
by 4.7 per cent.

This year, and for the first time in New Zealand, Fairfax Media is 
partnering with the Global Drug Survey to help create the largest and 
most up-to-date snapshot of our drug and alcohol use, and to see how 
we compare to the rest of the world.

The Dunedin study found an eight-point decline in the IQs of some 
early cannabis users. IQ points lost were not fully recovered when 
cannabis use ceased.

"What this all suggests is that adolescence is a very sensitive 
period in brain development and policymakers need to find ways of 
delaying cannabis use as much as possible for young people," Prof Poulton said.

However, researchers cannot definitely say cannabis is the cause of 
schizophrenia, Associate Professor Nadia Solowii, of the University 
of Wollongong, said.

Research showed the drug was known as a "component cause" in that it 
could trigger psychosis in vulnerable people, Prof Solowii said.

"Cannabis receptors are abundant in the human brain and are 
associated with higher functions such as attention, memory, learning 
and planning as well as pain, appetite and sleep," she said.

"Bombarding the brain with THC, the main psychoactive ingredient in 
cannabis, can interrupt the natural balance of cannabinoids in the 
brain and can produce very similar kinds of impairments to those 
suffering from schizophrenia, even in people not already prone to the 
disorder."

Cannabidiol, or CBD, is another psychoactive component of cannabis 
that is thought to counteract the short- and long-term negative 
effects of THC. However, CBD had largely been bred out of modern 
cannabis because of market demand for higher THC levels, Prof Solowii said.

This was likely to have increased the association between cannabis 
use and psychosis.

The Dunedin Longitudinal Study started 40 years ago, and closely 
follows the lives and health of 1037 babies born in 1972-73, 981 of 
whom are still involved and are now about 40.

Fairfax NZ
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MAP posted-by: Jay Bergstrom