Ariana Eunjung ChaJun 22, 2026 – 5.00amStephen Lankenau has spent years studying how people use cannabis in everyday life. As director of Drexel University’s Medical Cannabis Research Centre, he has watched legalisation spread, products grow stronger and daily use become increasingly common.Yet one of the most basic questions remains surprisingly difficult to answer: How much cannabis is too much for the brain?Washington PostSubscribe to gift this articleGift 5 articles to anyone you choose each month when you subscribe.Subscribe nowAlready a subscriber? Fetching latest articles