Early marijuana use tied to long-term brain problems

New research shows that adults who smoked marijuana before age 15 have significant problems with attention span, impulse control, and “executive function” – the ability to plan and carry out tasks.

How about people who took up toking later in life? The same research showed they were much less likely to have such difficulties.

http://www.cbsnews.com/8301-504763_162-20067999-10391704.html