Continued high use of marijuana by the United States' eighth, 10th and 12th graders combined with a drop in perceptions of its potential harms was revealed in this year's Monitoring the Future survey, an annual survey of eighth, 10th, and 12th-graders conducted by researchers at the University of Michigan. The survey was carried out in classrooms around the country earlier this year, under a grant from the National Institute on Drug Abuse, part of the National Institutes of Health.