the whole "study" is flawed how can a substance used 1 time permanently change the structure of your brain? its out of your system max in 30 days, I am thinking that those who did marijuana are more aware of there shortcommings and more willing to admit they may have a problem. also it doesent mention anything about the participants of the study, what was the circumstances? this commentary is far to vaugue to be taken seriously, also usually participants of such study's are either students or military personnell so the study will be skewed too reflect the positive aspects of the drug war, less somebody have a tracking ability on the piece of paper your responding on.