In a survey of 216,000 adolescents from all 50 states, the Washington University School of Medicine has found that marijuana use among 12- to 17-year-olds fell 24 percent from 2002 through 2013. In 2002, a little more than 16 percent of that age group reported using pot during the previous year; in 2013, the number fell below 14 percent.
Researchers concluded the declining use of weed was related to fewer teens being involved in disciplinary incidents in school and crime. Although they couldn’t be sure why, some researchers theorized that more young people receive treatment earlier for behavioral difficulties, leaving them less susceptible later to the lure of drugs and other dangers.