People who use marijuana prior to the age of 12 are twice as likely to experience a serious mental illness compared to those who first use marijuana at age 18 or older. for the first time, the survey measured daily marijuana vaping, which was reported at 3. 7 the chart below shows the percentage of teens who say they use marijuana. More teens are using high-potency cannabis products, which have the potential for increased negative health effects. Marijuana concentrate can have thc levels that range from 40 to 80 percent. Per day, 3,300 young adults (18-25) initiated the use of marijuana per day, 1,400 persons 26 and older initiated use of marijuana teens are increasingly using marijuana through vaping as it is easier to transport and hide. the survey also revealed that prevalence of annual teen marijuana use rose by 1. 3 percentage points, reaching almost 24 percent in 2017, based on combined responses from 8th, 10th and 12th graders. But, some risk behaviorssuch as using marijuanacan have harmful and long-lasting effects on a teens health and well-being. Unlike adults, the teen brain is actively developing and often will not be fully developed until the mid 20s. Marijuana use during this period may harm the developing teen brain. To see how teen marijuana use compares in states with and without such laws, researchers examined survey data on substance use collected from 861,082 adolescents in 45 states, aged 14 to 18 years. About 60 percent of kids who are using drugs admitted to using marijuana. This was in a period of one month and some used it for more than 20 days. More than 11 percent of eighth graders said they used marijuana in the past year. The monitoring the future survey also showed that teens perception of marijuanas harmfulness is down, which can signal future increases in. synthetic marijuana (often sold over the counter as k-2 or spice) continued its rapid decline in use among teens since its use was first measured in 2011. Among 12th-graders, for example, annual prevalence has fallen by more than two-thirds, from 11.