Did teen perception, use of marijuana change after recreational use legalized?

(The JAMA Network Journals) Marijuana use increased and the drug's perceived harmfulness decreased among eighth- and 10th-graders in Washington after marijuana was legalized for recreational use by adults but there was no change among 12th-graders or among students in the three grades in Colorado after legalization for adults there, according to a new study published online by JAMA Pediatrics.