Home  »  Science  »  Regular teenage marijuana use causes brain development damage


Jan 9, 2013 No Comments ›› spratico

NewYorkTimes-The most disturbing new studies about early teenage use of marijuana showed that young adults who started smoking pot regularly before they were 16 performed significantly worse on cognitive tests of brain function than those who had started smoking later in adolescence. They performed particularly poorly on tests assessing executive function, which is responsible for planning and abstract thinking, as well as understanding rules and inhibiting inappropriate responses.

Imaging scans also found detectable differences in how their brains worked, said Staci Gruber, the lead author of these studies and director of the cognitive and clinical neuroimaging core at the imaging center at McLean Hospital in Boston. Imaging scans found alterations in the frontal cortex white matter tracts of the brain in the early-starters, she said, that are associated with impulsiveness.

“The frontal cortex is the last part of the brain to come online, and the most important,” Dr. Gruber said. “Early exposure perhaps changes the trajectory of brain development, such that ability to perform complex executive function tasks is compromised.”

A recent study showing a drop in IQ scores among teenagers who are regular pot smokers is especially troubling, Dr. Evins said. A more recent study found that people who started smoking marijuana as teenagers and used it heavily for decades lost IQ points over time, while those who started smoking as adults did not, though some critics have said these differences may not be meaningful. Older survey studies had indicated that regular pot smokers were less likely to graduate from high school or pursue higher education, but it was never clear which came first, difficulty in school or the drug use.

“If parents who are spending thousands of dollars on SAT prep courses knew about the cognitive effects marijuana has on their kids’ brains, they would be up in arms,” Dr. Evins said. Other health concerns about marijuana are less well documented but may turn out to be significant. States that legalized marijuana prohibit driving under its influence, and studies have found marijuana smoking increases weaving between lanes and slows reaction times. And although marijuana is not as damaging to the lungs as tobacco, in part because people do not smoke a pack of joints a day, a regular habit can eventually take a toll on the lungs.

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