Picture the stereotypical pot smoker: young, dazed and confused. Marijuana has long been known for its psychoactive effects, which can include cognitive impairment. But new research published in June in Nature Medicine suggests the drug might affect older users very differently than young ones—at least in mice. Instead of impairing learning and memory, as it does in young people, the drug appears to reverse age-related declines in the cognitive performance of elderly mice.