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But the survey by the Substance Abuse and Mental Health Services Administration (SAMHSA) shows young adults 18 to 25 are using more prescription drugs.

Use of prescription pain relievers for non-medical purposes in that age group rose from 4.1% in 2002 to 4.6% in 2007.

Drug use increased among Baby Boomers, primarily use of marijuana. For those age 50 to 54, the rate of illicit drug use increased from 3.4% in 2002 to 5.7% in 2007.

The rates for those 55 to 59 increased from 1.9% to 4.1% in 2007.

"There probably is a group of boomers who maybe in their 20s used pot and maybe never stopped," says Peter Delany, who is director of the office of applied studies for SAMHSA.

"We're making significant progress in a number of areas," he says, but "we still have a long way to go."

The latest National Survey on Drug Use and Health is based on interviews with nearly 68,000 people, all interviewed in their homes from January through December 2007.

Overall, about 20 million people 12 and older reported using illicit drugs in the past month.

Steve Pasierb, CEO of the Partnership for a Drug-Free America, a non-profit organization that focuses on reducing drug use among young people, says the survey reflects his organization's data.

"This generation is abusing far fewer illegal drugs than any generation before them," Pasierb says, but "prescription drugs are a problem."

Kids and parents often don't recognize prescription drugs as a problem because they're legal, he says. But they can be as dangerous as any street drug when taken without a prescription for non-medical reasons.

"We don't have parents tuned into this issue the way we have parents tuned into other forms of drug use," Pasierb says.

The prescription drug issue is especially important because "the numbers of kids abusing prescription drugs dwarfs the numbers of kids using all other drugs combined except marijuana and alcohol," says Joseph Califano, president of the National Center on Addiction and Substance Abuse (CASA) at Columbia University.

"If you're a parent, you can certainly take some comfort in the fact that there's some decrease in the use of methamphetamines, cocaine and marijuana," Califano says, "but you should take no comfort in the fact that we're continuing to see significant increases in prescription drug abuse."