One factor behind the growth is that people can get the drugs easily from doctors, friends, relatives and through the Internet, according to a study by the National Center on Addiction and Substance Abuse at Columbia University in New York City.
Relying on various government reports, the study cited rapidly rising rates of abuse of prescription drugs, especially among teenagers.
About 15 million people in the United States abused controlled prescription drugs, and the amount of abuse has gone up sharply over the past decade among all adults and especially among teens, according to the center's analysis of federal data.
Prescription drug abuse is defined in the study as the taking of prescription drugs for reasons not prescribed for the user or use of prescription drugs only for the experience or feeling it causes.
"We have an epidemic of abuse of painkillers," said Joseph Califano Jr., the center's chairman and president. "The problem with teens is a far more serious problem than anyone has ever realized."
Many doctors and pharmacists surveyed by the center said they have received only limited training in prescribing drugs.
Four in 10 doctors said they were not trained in medical school how to prescribe controlled substances; more than half had no training on how to identify prescription drug abuse or addiction. Three-fourths said they had had no training in medical school identifying diversion of prescription drugs for illicit purposes.
The separate polls of 979 physicians and 1,030 pharmacists were conducted during the summer of 2004. Each has a margin of error of plus or minus 3 percentage points.