Marijuana Plant (IMAGE) Washington University School of Medicine Caption Researchers at Washington University School of Medicine in St. Louis have found that the number of teens with marijuana-related problems, and the percentage using the drug, have declined even as states have legalized and decriminalized pot. Credit BRETT LEVIN Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.