Study suggests pot use in early teens can harm cognitive function

Although pot is often held up as a more benign intoxicant than alcohol, it does seem to pose a bit of a risk to teens who pick up the practice at a younger age.

The author of the study, which was conducted at McLean Hospital in Massachusetts, said the effects of chronic marijuana usage could be more pronounced in those who began using the drug at a younger age:

“We have to understand that the developing brain is not the same as the adult brain,” said Dr. Staci A. Gruber, the paper’s senior author and director of the cognitive and clinical neuroimaging section of the neuroimaging center at McLean, a Harvard-affiliated hospital in Belmont, Mass.

The study was small, performed on just 35 stoners, 20 of whom had begun smoking before the age of 16 and 15 who had started smoking regularly after that age. Education and income levels were controlled for, and brain scans were part of data collected in the study. Marked differences were measured in the longer-term pot smokers than the ones who picked up the pipe at a later date:

The subjects were asked to complete an assessment of executive function — the brain processes responsible for planning and abstract thinking, as well as understanding rules and inhibiting inappropriate actions… The participants who started smoking marijuana at younger ages scored significantly lower on the test than those who started smoking later in their teen years, Dr. Gruber said. They got fewer of the card-sorting categories correct and made more mistakes. They were also much more likely to repeat their mistakes, continuing to give incorrect answers even after being told that they were wrong.

Dr. Gruber said the portion of the brain that “modulates executive function is the last part to develop,” and that per the data, age restrictions on legal marijuana should be considered.