People who started smoking marijuana at a young age did much worse on tests of executive brain function than those who started smoking when they were older, a new study shows.
The findings highlight the danger posed by marijuana and the need to develop effective strategies to reduce marijuana use, especially among young people, said the researchers. They noted that adolescence is a critical time in brain development.
Executive function includes planning, flexibility, abstract thinking and inhibition of inappropriate responses.
Dagga users studied
The study of 33 chronic marijuana smokers and 26 nonsmokers found that, overall, habitual marijuana users appeared less able to maintain focus and were more likely to make errors.
Those who started smoking before age 16 made twice as many mistakes on tests of executive function as those who started smoking the drug after age 16. The early-onset users also smoked three times as much marijuana per week and twice as often as the late-onset users.
"Our data suggest that the earlier you begin smoking, the more marijuana you smoke and the more frequently you smoke. That's an important finding," study author Staci A. Gruber, director of the Cognitive and Clinical Neuroimaging Core at McLean Hospital in Belmont, Mass.m, and an assistant professor of psychiatry at Harvard Medical School, said.
"We have to be clear about getting the message out that marijuana isn't really a benign substance," she added. "It has a direct effect on executive function. The earlier you begin using it, and the more you use of it, the more significant the effect."
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