Australian scientists say they have proved that persistent heavy marijuana use damages the brain’s memory and learning capacity. Their study showed for the first time the earlier people developed a cannabis habit, the worse the damage.

Scientists from Melbourne’s Murdoch Childrens Research Institute (MCRI), Melbourne University and Wollongong University used Magnetic Resonance Imaging (MRI) to scan the brains of 59 people who had been using marijuana for 15 years on average. The images were compared with scans of 33 healthy people who had never used the drug.

via Marijuana and memory: study shows it’s not good news.