A new study explores the effects of both recent and lifetime cannabis use on brain function during cognitive tasks. The study, the largest of its kind ever to be completed, examined the effects of cannabis use on over 1,000 young adults aged 22 to 36 using brain imaging technology. The researchers found that 63% of heavy lifetime cannabis users exhibited reduced brain activity during a working memory task, while 68% of recent users also demonstrated a similar impact. This decline in brain activity was associated with worse performance on working memory -- the ability to retain and use information to perform tasks. For example, working memory allows a person to follow instructions they've just been given or to mentally visualize and manipulate information, like solving a math problem.