Teens are smoking and drinking less, though teens in states that legalized marijuana for medical use report a higher use of marijuana-infused edibles, according to the latest results of an annual study funded by the National Institutes of Health.



Six percent of high school seniors use marijuana daily, said the long-running study, which surveyed eighth, 10th and 12th graders in public and private schools. Just under 23 percent of high school seniors said they had used marijuana in the past month.



Among eighth graders, marijuana use in the past month dropped to 5.4 percent from 6.5 percent in 2015. Daily usage dropped to 0.7 percent from 1.1 percent in 2015, and past year marijuana use among eighth graders dropped to 9.4 percent from 11.8 percent in 2015.



"Similarly, rates of marijuana use in the past year among 10th graders also remained stable compared to 2015, but are at their lowest levels in over two decades," a release on the survey from the National Institute on Drug Abuse said.

Massachusetts legalized marijuana. What happens next?



Massachusetts legalized medical marijuana in 2012, and last month voters approved marijuana for recreational use. The new law goes into effect on Dec. 15, allowing adults over the age of 21 to possess and grow marijuana. Marijuana remains illegal under federal law.



Among teens in states with medical marijuana, 40.2 percent of seniors said they ate marijuana-infused food in the past year. In states without medical marijuana, the number was 28.1 percent of seniors.

No change to marijuana effective date of Dec. 15 in Mass.



The institute noted a "large drop" in teens using tobacco cigarettes across the three grades. Among high school seniors, 1.8 percent said they smoked a half pack or more a day, down from 10.7 percent in 1991.



Usage of alcohol has also dropped, with the rate of teens saying they've been drunk in the last year dropping to the survey's "lowest rates ever," the institute said. In 2001, 53.2 percent of seniors said they'd been drunk at least once; now the number is 37.3 percent.



The survey included 45,473 students from 372 public and private schools.



"The declining use of many drugs by youth is certainly encouraging and important," Dr. Lloyd Johnston, who has worked on the survey of teens at the University of Michigan's Institute for Social Research, said in a statement.



"But we need to remember that future cohorts of young people entering adolescence also will need to know why using drugs is not a smart choice," he added. "Otherwise we risk having another resurgence of use as was seen in the 90s."