"I'm a little worried that we may be seeing the leading edge of a trend here," said Sean Clarkin, director of strategy at The Partnership for a Drug-Free America, which was releasing the study. "Historically, you do see the increase in recreational drugs before you see increases in some of the harder drugs."
The annual survey found the number of teens in grades 9 through 12 who reported drinking alcohol in the last month rose 11 percent last year, with 39 percent about 6.5 million teens reporting alcohol use. That's up from 35 percent, or about 5.8 million teens, in 2008.
For pot, 25 percent of teens reported smoking marijuana in the last month, up from 19 percent.
CBSNews.com Special Report: Marijuana Nation
Until last year, those measures for pot and alcohol use had been on a steady decline since 1998, when use hovered around 50 percent of teens for alcohol and 27 percent for pot.
The study also found use of the party drug Ecstasy on the rise. Six percent of teens surveyed said they used Ecstasy in the past month, compared with 4 percent in 2008.
Meanwhile, a separate study in Australia found a possible link between long-term marijuana use and among young people.
According to the findings, published Monday in the journal Archives of General Psychiatry, those who reported smoking marijuana for six or more years were twice as likely to develop a psychosis, such as schizophrenia, and four times as likely to get high scores in clinical tests of delusion.
If parents suspect their teen is using, they need to act quickly, Clarkin said. Monitor them more closely, talk with them about drugs, set rules and consult outside help, like a counselor, doctor, clergy or other resource, he said.
The researchers asked teens how they felt about doing drugs or friends who did them. The study found a higher percentage of teens than in the previous year agreed that being high feels good; more teens reported having friends who usually get high at parties; and fewer teens said they wouldn't want to hang around kids who smoked pot.
Stacy Laskin, now 21 and a senior in college, said marijuana was everywhere during her high school years. Laskin said she tried pot and drank alcohol in high school, but didn't make it a habit like other kids she knew.
"The behavior I saw people go through and to see how far people can fall really turned me away more than anything else," Laskin said in an interview with The Associated Press.
Her close friend from high school died in 2008 from a heroin overdose. Laskin, a psychology major at Salisbury University in Maryland, was so torn by her friend Jeremy's death that she decided to help others and is working on her second internship at a drug treatment center.
"Just seeing the negative impact made me want to get involved," she said.
• Teen abuse of prescription drugs and over-the-counter cough medicine remained stable from 2008 to 2009. About 1 in 7 teens reported abusing a prescription pain reliever in the past year; and about 8 percent of the teens questioned reported over-the-counter cough medicine abuse in the past year.
• Teen steroid and heroin use remained low at 5 percent for lifetime use.
The Partnership's "attitude tracking" study was sponsored by MetLife Foundation. Researchers surveyed 3,287 teens in grades 9 through 12. Data were collected from questionnaires that teens filled out anonymously from March to June 2009. The study has a margin of error of plus or minus 2.3 percentage points.
The New York-based Partnership is a nonprofit group working to reduce the use of illicit drugs.