Prescription-drug abuse in the USA declined last year year to the lowest rate since 2002 amid federal and state crackdowns on drug-seeking patients and over-prescribing doctors.

Young adults drove the drop. The number of people 18 to 25 who regularly abuse prescription drugs fell 14% to 1.7 million, the National Survey on Drug Use and Health reported Monday. In 2011, 3.6% of young adults abused pain relievers, the lowest rate in a decade.

The survey, sponsored by the Substance Abuse and Mental Health Services Administration, collects data from interviews with 67,500 people age 12 and older.

Administrator Pamela Hyde said the decrease in abuse indicates that public health and law enforcement efforts to curb abuse of prescription drugs, such as the powerful painkillers oxycodone and hydrocodone, work.

In 2011, 6.1 million people abused narcotic pain pills, tranquilizers, stimulants and sedatives, down from 7 million people in 2010, the survey found. Pain pill abuse dropped from 2.1% of the population in 2009 to 1.7% in 2011.

Still, the number of people addicted to pain relievers grew from 936,000 in 2002 to 1.4 million in 2011. About a third of the addicts are 18 to 25, the survey found.

Most states operate prescription-drug monitoring programs, which can identify doctors who prescribe excessive doses of the drugs and patients who seek multiple prescriptions from different doctors, said Gil Kerlikowske, director of the White House Office of Drug Control Policy.

In 2011, 22.5 million Americans 12 or older, nearly 9% of the population, said they regularly used illicit drugs such as marijuana, cocaine, heroin, hallucinogens and inhalants or abused prescription drugs, including pain relievers, tranquilizers, stimulants and sedatives. While cocaine abuse has dropped from 2.4 million regular users in 2006 to 1.4 million last year, heroin abuse is rising, the survey found. The number of people who reported regular heroin use grew from 161,000 in 2007 to 281,000 in 2011, the survey found.

Marijuana remains the most commonly abused drug at all ages. Among youth, while drinking and smoking declined, marijuana use grew steadily since 2008, the survey found. Another study, Monitoring the Future, which surveys students in eighth and 10th grades, has also noted increasing marijuana use. That study found that 12.4% of eighth- and 10th-graders had used marijuana in the previous month, the highest rate since 2003.

"Marijuana is still bad news," Kerlikowske said.

Just 44.8% of teens think smoking marijuana is risky, down from 54.6% in 2007, he said. Voter initiatives to legalize and regulate marijuana send a message that marijuana is medicine, Kerlikowske said.

"I think they are getting a bad message on marijuana," he said. "I think that the message that it's medicine and should be legalized is a bad message.

Ethan Nadelmann, executive director of the Drug Policy Alliance, which advocates legalizing marijuana and treatment over incarceration, says the U.S. should focus on public health initiatives to curb drug use, reduce overdoses and halt the spread of HIV and hepatitis.

"It's good to see problematic use of alcohol and tobacco among young people continuing to decline -- and worth noting that this good news has little to nothing to do with arrests, incarceration or mandatory drug testing," Nadelmann said. "Contrast this with marijuana use, which has increased somewhat notwithstanding the fact that almost 800,000 people are arrested each year for marijuana possession."

USA Today