The study, appearing the Journal of the American Medical Association, found that nearly two-thirds of the West Virginians who died from overdoses in 2006 were killed by medications they did not have a prescription for. At the same time, nearly all the people who died had a prior history of abusing medication.

"I think it's fair to say based on the study, prescription drugs are driving the drug mortality epidemic, especially in West Virginia," said the Dr. Aron Hall of the Centers for Disease Control.

Hall, the lead author of the study, formerly was the CDC's Epidemic Intelligence Service officer assigned to West Virginia. One figure that struck him was from an earlier study that found that drug overdose deaths in the Mountain State increased 550 percent from 1999 to 2004, the highest in the nation and more than twice as high as the second-ranked state, Oklahoma.

At the same time, the state had two tools that gave the researchers a rare opportunity to learn what was causing the spike. One was a centralized medical examiner system. The other was a prescription medication-monitoring program.

By focusing on overdose deaths in 2006, Hall and the other researchers reached the following conclusions:

• Two-thirds of the 295 overdose deaths were men, and more than 90 percent of all deaths were among people age 18 to 54.
• Painkillers were used by 275 of the people who died from overdoses, less than half of which had a prescription for the medication.
• People between the ages of 18 to 24 were most likely to have obtained medications without a prescription.
• Women who died from overdoses were twice as likely as men to have used doctor shopping to obtain their medications. Doctor shopping was defined as having seen five or more clinicians in the year prior to their deaths.
• People who used doctor shopping were most likely to have been between the ages of 35 to 44.
• The painkiller methadone was used in 40 percent of the deaths, more than any other single drug.
• Nearly 95 percent of the people who died from overdoses had at least one indicator suggesting they were at higher risk for substance abuse, such as a past history of drug or alcohol abuse.

As for the reasons for the high number of overdoses, the authors noted that abuse of painkillers has been linked to Medicaid eligibility and low income, with West Virginia the third poorest state.

Hall said that from a policy level, state officials should concentrate most on prescription drug abuse when combating overdose deaths, given illegal drugs and alcohol accounted for relatively few overdoses in comparison.

Also, he noted nearly all the people who died from overdoses had indicators of past substance abuse, "so this is clearly a group that had an opportunity to be identified."