Study: Younger Users of Marijuana at Higher Risk of Brain Damage

A small study performed by researchers at McLean Hospital in Boston suggests that children who start using marijuana before age 16 are at higher risk of long-term brain damage than those who start later, The Boston Globe reported Nov. 16.

The study tested the mental flexibility and focus of 59 young people from Boston, of whom 33 used marijuana. Among those tested, smokers who began using before age 16 had significantly impaired abilities to perform simple tasks, when compared to other users and to non-users.

In addition, users who began smoking marijuana before age 16 consumed three times as much of it each week than did smokers who started using after age 16.

“If we know the developing brain is sensitive to drugs and we see a direct relationship between early exposure to marijuana and [cognitive] performance, we have to let people know we need to perhaps impose guidelines, like you can’t do this until you're 21, [as with] cigarettes and drinking,” said Staci Gruber, the study's leader.

Gruber, an assistant professor of psychiatry at Harvard Medical School, directs the Cognitive and Clinical Neuroimaging Core at McLean Hospital.

The study’s results are to be shared at the upcoming Neuroscience 2010 conference and will soon be submitted to a scientific journal. It has not yet been peer-reviewed.