Pubdate: Sat, 18 Jun 2005
Source: Calgary Herald (CN AB)
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Copyright: 2005 Calgary Herald
Contact:  http://www.canada.com/calgary/calgaryherald/
Details: http://www.mapinc.org/media/66
Author: Roger Highfield, The Telegraph (UK)

POT USERS RISK LATER ADDICTIONS

Study shows chronic use by teens affects brain development

Teenagers and young adults who occasionally smoke cannabis over long periods
are more likely to turn to more addictive drugs such as heroin, according to
a study.

While it has been assumed the brain is almost fully formed by the time
children reach their teens, there is evidence the brain continues to develop
until as late as age 25.

Experiments on rats by Prof. Yasmin Hurd, of the Karolinska Institute,
Sweden, show that chronic periodic use of cannabis can interfere with brain
development.

If confirmed, the findings suggest that children and young adults who use
the drug over long periods would be more prone to anxiety and more dependent
on anxiety-reducing drugs.

Hurd's experiments show that, after training to self-administer heroin by
pushing a lever, rats exposed to THC took more heroin as adults than those
not given the chemical. They were more sensitive to lower concentrations of
heroin than unexposed rats and took more in response to stress.

"The developing brain is definitely more sensitive," she said. "Many people
think that all cannabis does is to give you a calm, relaxed feeling and no
long-term effects." Given the brain effects and link between smoking and
lung cancer, she questioned "why governments would want to decriminalize
this drug."

Despite its widespread use, Hurd believes there is still much to be learned
about pot. "Cannabis may be less addictive than, for example, cocaine or
heroin, but it is still a drug."

Prof. Robin Murray, of the Institute of Psychiatry in London, said that,
while the research needs to be replicated, it indicates "it may be easier to
come to grief when you try heavy drugs if you have already sensitized your
brain receptors with cannabis."
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MAP posted-by: Josh