WEDNESDAY, Dec. 14, 2011 (HealthDay News) -- Alcohol use by American teens has dropped to historic lows, but more of them are using marijuana and don't believe it's a dangerous drug, according to an annual national survey conducted by the U.S. National Institute on Drug Abuse and the University of Michigan.
The nationally representative survey of 47,000 students in grades eight, 10 and 12 at 400 public and private schools found a continuing trend of lower alcohol consumption that stretches back to the 1980s.
Forty percent of 12th graders reported drinking within the previous 30 days in the new survey, compared to 54 percent in 1991. And rates declined from 43 percent to 27 percent among 10th graders, and from 25 percent to 13 percent among eighth graders.
The 2011 Monitoring the Future survey also found evidence of declines in teens' use of illicit drugs such as cocaine, crack cocaine and inhalants, as well as illegal use of the narcotic drug Vicodin, the stimulant drug Adderall, sedatives, tranquilizers, and cough and cold medicines.
But, marijuana use among teens rose in 2011 for the fourth straight year, after a large decline in the preceding decade.
The number of teens in all three grades who said they had used marijuana in the past year increased from 21.4 percent in 2007 to 25 percent in 2011. Rates of daily or near daily marijuana use have also increased in all three grades and this year were 1.3 percent in grade eight, 3.6 percent in grade 10, and 6.6 percent in grade 12.
"Put another way, one in every 15 high school seniors today is smoking pot on a daily or near daily basis," principal investigator Lloyd Johnston said in a University of Michigan news release. "And that's the highest rate that we have seen over the past 30 years -- since 1981."
The increasing use of marijuana may be due to the fact that fewer teens believe the drug is dangerous, even with regular use, the researchers said. This "perceived risk" among teens has fallen sharply over the past five years and continued to decline this year, the survey found.
In addition, teens' disapproval of marijuana use has declined over the past three or four years, which suggests there is less peer pressure to discourage use of the drug.
The U.S. National Institute on Drug Abuse offers marijuana facts for teens.