Pubdate: Fri, 17 Oct 2014
Source: Globe and Mail (Canada)
Copyright: 2014 The Globe and Mail Company
Contact:  http://www.theglobeandmail.com/
Details: http://www.mapinc.org/media/168
Author: Adriana Barton
Page: L7

POT AND THE TEENAGE BRAIN: UNDERSTANDING THE SCIENCE

Because their brains are still developing, adolescents may be 
particularly vulnerable to the negative effects of marijuana.

During this crucial period, brain connections are strengthened 
through myelination - growth of fatty insulation around the neurons - 
as well as a "pruning" of inefficient neural connections. It's a 
lengthy process, stretching past the postsecondary years to at least 25.

Hundreds of studies have been conducted in recent decades to 
determine how cannabis affects youth.

While not all research has shown harms, study after study - including 
a large review released Oct. 7 in the journal Addiction - has linked 
regular pot use in adolescence to detrimental effects ranging from 
worse education outcomes to cognitive impairments and losses in IQ.

Some pot advocates suggest that research has been skewed by anti-drug 
organizations that only fund studies looking for harms. Others argue 
that marijuana is less harmful to teens than opiate drugs or alcohol, 
and that negative effects in heavy cannabis users have been 
generalized to light recreational users.

Still others point to inconsistent results in some studies. One 
explanation, researchers say, is that participants' marijuana use was 
largely self-reported and the dosage of the psychoactive ingredient 
tetrahydrocannabinol (THC) might have varied widely depending on 
which strains they were smoking.

Still, scientists have been unable to prove without a doubt that 
marijuana is the direct cause of a child's low motivation or learning 
problems. And they may never have ironclad proof since randomized 
controlled trials, the gold standard of scientific research, are not 
possible in marijuana studies involving youth for the simple reason 
that scientists can't ethically assign a group of children to take 
regular doses of cannabis, compare them to a drug-free control group, 
and see how they turn out.

Instead, scientists have relied on long-term studies in which 
participants, followed since birth, serve as their own controls.

Now, scientific consensus that marijuana is harmful to the developing 
brain is so strong, concerns about teen cannabis use can no longer be 
dismissed as a modern-day version of "reefer madness" propaganda, 
substance-abuse experts say.
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