The latest Monitoring the Future Panel Study by principal investigator John Schulenberg, professor of psychology and research professor at the Institute for Social Research, found that 43 percent of college-age adults, including those not in school, use marijuana – the highest level in nearly four decades: “Daily marijuana use is a clear health risk. The brain is still growing in the early 20s, and … scientific evidence indicates that heavy marijuana use can be detrimental to cognitive functioning and mental health.”