Very Heavy Pot Use Clouds Mental Function: Study 1 hour, 58 minutes ago By Dana Frisch NEW YORK (Reuters Health) - 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...