Smoking Pot Impairs Brain Development say Harvard Study
The study shows that smoking marijuana before the age of 16 leaves individuals with weakened executive function, such as planning, flexibility and abstract thinking.
One of the tests conducted as part of the study included subjects being asked to sort a deck of cards following one set of rules, and then quickly switching to another set of rules without warning. The individuals who started smoking at an early age performed significantly worse than non-users and those who started using marijuana later in life.
In other tests, early marijuana users continued to make the same errors repeatedly.
Previous studies by neuroscientists had shown that those who smoke large amounts of marijuana on a regular basis do not do well on tests of memory and other mental abilities.