Sorry . . . what were you saying? Oh, yes: A massive neuroimaging study led by researchers at the University of Colorado found that huge majorities of young adult marijuana users suffer significant cognitive impairment in everyday life. Specifically, 63% of heavy lifetime users and 68% of recent users experienced reduced brain activity, which is associated with performance issues, while doing working-memory tasks (i.e. those that require you to retain and use information to get the job done). This is the largest study of its kind ever done; this isn’t a statistical fluke. Seems like the haze isn’t only coming from all the smoke in users’ eyes.