Teenagers are now using marijuana more than alcohol, according to the latest Monitoring the Future Survey performed in conjunction with the National Institute of Drug Abuse.

Every year since 1975 researchers from the University of Michigan have been conducting the MTF survey among approximately 50,000 teenagers in the eighth, 10th, and 12th grades, to determine their attitudes and behaviors regarding drugs, alcohol, and cigarettes. This year the research team found that alcohol use was at historical lows, but use of marijuana was the highest in 30 years. One in 15 teenagers uses it daily, the highest number since 1981. About 36% of high school seniors used marijuana in the past year or, compared to 31% in 2007. One in four high school seniors smoked pot within the past month, and one in five 8th graders experimented with the drug at least once in the past year. These figures represent the fourth straight year of increases in teenage marijuana use.

One explanation is that teenagers perceive marijuana to be safer than alcohol, partly because of the current discussion about medical marijuana. Sixteen states have already legalized marijuana for medical purposes. Teenagers tend to believe that prescription drugs are safer than street drugs, even though prescription drugs can be just as dangerous and addictive. They now believe marijuana is safer than alcohol. The MTF survey found that 2500 teenagers experiment with prescription drugs every day for the first time.

“One thing we have learned over the years is that when young people come to see a drug is dangerous, they are less likely to use it,” said Lloyd Johnston, the principal investigator in the MTF survey. “This helps to explain why marijuana right now is rising, because the proportion of kids who see it as dangerous has been declining.”

Another reason why marijuana may be on the increase is that teenagers 20 years ago were using marijuana at high rates, and now that they are parents themselves, they may still be using it , and/or they have a relaxed attitude about it. Marijuana use is increasing in the general population, especially since a new synthetic form has become more widely available. The federal government has recently reacted to that situation through an emergency order that bans the sale of five chemicals used in herbal blends to make synthetic marijuana. So far, this measure is so new that it did not affect the results of the MTF survey, which found that one in nine teens has tried synthetic marijuana.

The increasing use of marijuana may also be linked to the fact that roughly one in three Americans under age 23 years old has been arrested for a non-traffic offense, according to new research published in the journal Pediatrics. The authors believe that the real rate may be closer to 41%, because many cases are undocumented.

This new study from the University of North Carolina in Charlotte used data from the National Longitudinal Survey of Youth and found that there has been more aggressive treatment of offenders and that more people are being put in prison since the 1960s. In the 1960s, the number of U.S. prisoners was about 100 per 100,000 people, but today it is 500 inmates per 100,000.

The new study found that the risk for being arrested was the greatest during late adolescence or emerging adulthood. Lead researcher Dr. Richard Brame believes that pediatricians should intervene whenever possible.

“We don’t think that kids get arrested in isolation, we’re assuming that other issues are going on in their lives and we want pediatricians to be aware and try to understand and start a broader discussion about what’s going on in the lives of young people,” Dr. Brame said.

Dr. Paula Braverman, chair of the Committee on Adolescence of the American Academy of Pediatrics, agreed that pediatricians could bring up issues during routine check-up visits.

“Pediatricians have an opportunity to identify risk factors that are associated with increased chances of involvement in behaviors that can lead to delinquency,” she said. “We’re asking about school, what’s going on in the family. We’re asking about drug use and we’re screening for mood and mental health issues.” She said that pediatricians might be able to make referrals for mental health services for teenagers and children at risk for criminal behaviors.