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. - --- MAP posted-by: Jay Bergstrom