Long-Term Marijuana Use Linked to Changes in Brain's Reward System

People who use marijuana for many years respond differently to natural rewards than people who don't use the drug, according to a new study. Researchers found that people who had used marijuana for 12 years, on average, showed greater activity in the brain's reward system when they looked at pictures of objects used for smoking marijuana than when they looked at pictures of a natural reward — their favorite fruits. "This study shows that marijuana disrupts the natural reward circuitry of t