Pubdate: Sat, 18 Jun 2005
Source: Daily Telegraph (UK)
Copyright: 2005 Telegraph Group Limited
Contact:  http://www.telegraph.co.uk/
Details: http://www.mapinc.org/media/114
Author: Roger Highfield
Bookmark: http://www.mapinc.org/pot.htm (Cannabis)
Bookmark: http://www.mapinc.org/youth.htm (Youth)

LONG-TERM USE OF CANNABIS 'LEADS TO HARDER DRUGS'

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 that the brain is almost fully formed by the
time children reach their teens, there is evidence that the brain
continues to develop until as late as 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.

"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 decriminalise this drug".

Despite its widespread use, Prof Hurd believes there is much still to
be learnt about cannabis. "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:
"Clearly it needs to be replicated but there is already evidence that,
in animals, cannabis and amphetamine show cross-tolerance. So that
rodents given THC, the active ingredient of cannabis, show greater
effects when given amphetamine.

"This suggests that it may be easier to come to grief when you try
heavy drugs if you have already sensitised your brain receptors with
cannabis. We need more basic and clinical research into the long-term
effects."

The sites in the brain where cannabis act, called cannabis receptors,
affect both the production of the brain's "feel good chemicals" linked
with rewards.

Prof 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.
- ---
MAP posted-by: Larry Seguin