Donna Leinwand Leger

USA TODAY

Marijuana use among teens declined this year even as two states, Colorado and Washington, legalized the drug for recreational use, a national survey released Tuesday found.

University of Michigan's Monitoring the Future study, now in its 40th year, surveys 40,000 to 50,000 students in 8th, 10th and 12th grade in schools nationwide about their use of alcohol, legal and illegal drugs and cigarettes.

"There is a lot of good news in this year's results, bu the problems of teen substance use and abuse are still far from going away," Lloyd Johnston, the study's principal investigator, said.

After five years of increases, marijuana use in the past year by students in all three grades declined slightly, from 26% in 2013 to 24% in 2014. Students in the two lower grades reported that marijuana is less available than it once was, the survey found. Among high school seniors, one in 17, or 5.8%, say they use marijuana almost daily this year, down from 6.5% in 2013.

Synthetic marijuana, chemical concoctions meant to simulate a marijuana high and sold at convenience stores and gas stations, have also fallen out of favor. In 2011, when the survey first asked about the drugs, known as K2 and Spice, 11% of 12th graders said they had used the drugs in the past year. In 2014, that number had dropped to 6%.

"Efforts at the federal and state levels to close down the sale of these substances may be having an effect," Johnston said.

Abuse of all prescription drugs, including narcotic painkillers, sedatives and amphetamines, declined from 16% in 2013 to 14% in 2014 among 12th graders, the survey found. Narcotic painkiller use, in decline since 2009, dropped again from 7% in 2013 to 6% in 2014. Heroin use, which has grown among adult populations, remained stable for teens.

Teens considered narcotic pain relievers, such as OxyContin and Vicodin, safer than illicit drugs such as heroin and cocaine, because they are prescribed by doctors, Nora Volkow, director of the National Institute on Drug Abuse, said.

"There's a very strong and aggressive campaign about educating the public on the risk of opioid medications as it relates to overdoses and deaths," Volkow said. "That has made teenagers aware that they are not so safe as they thought they were."

Teen use of both alcohol and cigarettes dropped this year to their lowest points since the study began in 1975, the survey found.

Teens may be trading conventional cigarettes for e-cigarettes. In 2014, more teens used e-cigarettes than traditional tobacco cigarettes or any other tobacco product, the study found

"E-cigarettes have made rapid inroads into the lives of American adolescents," Richard Miech, a senior investigator of the study, said.

The survey asked students whether they had used an e-cigarette in the past 30 days. It is the first year the survey has asked about the product. Among 8th graders, 9% reported using an e-cigarette, while 4% reported smoking a tobacco cigarette. Among 12th graders, 16% said they used an e-cigarette compared to 7% for tobacco.

Two studies find big jump in teen use of e-cigarettes

Alcohol use and binge drinking peaked in 1997, when 61% of the students surveyed said they had drunk alcohol in the previous 12 months. In 2014, 41% reported alcohol use in the previous year, a drop from 43% in 2013, the survey found.

Since the 1997 peak, "there has been a fairly steady downward march in alcohol use among adolescents," Johnston said.

Binge drinking, defined as consuming five or more drinks in a row at least once in the two weeks before the survey, fell to 12% among the three grades in 2014 from 22% in 1997. Still, 1 in five high school seniors reported binge drinking this year, the survey found.

"Even though the indicators are very good news, at the same time we cannot become complacent," Volkow said. "This is a stage where their brains are most vulnerable. We need to continue our prevention efforts."