] "People who smoked unusually large amounts of marijuana
] performed worse on tests of mental function than their
] peers who smoked less pot, even after a 30-day abstinence
] period, according to a new report.
]
] Heavy users performed worse on 69% of the 35 tasks than
] light users, though their performances were not
] "clinically abnormal," the researchers found. The 22
] participants were admitted to hospital during the course
] of the study and submitted to random urine tests to
] ensure they remained abstinent."

Very Heavy Pot Use Clouds Mental Function: Study