Could smoking marijuana actually boost brain function in old age? According to a new British study out in the American Journal of Epidemiology – people age 50 who have a history of smoking pot scored on par or even much better on mental function and memory tests than their pot-free peers. Over 9,000 Britons were tested in the study – and as Reuters reports, “the study found, there was no evidence that current or past drug users had poorer mental performance. In fact, when current and past users were lumped together, their test scores tended to be higher.”