In a paper that will be presented on Monday, Nov. 15 at the annual meeting of the Society for Neuroscience in San Diego, Staci A. Gruber, PhD, reported that subjects who started using marijuana before age 16 made twice as many mistakes on tests of executive function, which includes planning, flexibility, abstract thinking and inhibiting inappropriate responses as those who began smoking after age 16.
"They performed significantly worse," said Gruber, director of the Cognitive and Clinical Neuroimaging Core at McLean and assistant professor of Psychiatry at Harvard Medical School.
The early-onset users also smoked three times as much marijuana per week and twice as often compared to the later-onset users, she
"Our data suggest that the earlier you begin smoking, the more marijuana you smoke and the more frequently you smoke," she
"That's an important finding."
said the findings are particularly critical today when legalization of marijuana is being considered in a number of states.
"We have to be clear about getting the message out that marijuana isn't really a benign substance," she
"Our results provide further evidence that marijuana use has a direct effect on executive function and that both age of onset and magnitude of marijuana use can significantly influence cognitive processing," said Gruber
"Given the prevalence of marijuana use in the United States, these findings underscore the importance of establishing effective strategies to decrease marijuana use, especially in younger populations," she