MONDAY, March 3, 2014 (HealthDay News) -- One of every three Tennesseans fills a prescription for narcotic painkillers at least once a year, creating a free-floating pool of available medication that helps feed the state's growing problem with prescription drug abuse, a new study has found.

Nearly 5.2 million Tennessee residents received painkillers -- 37 million total prescriptions -- between 2007 and 2011, which works out to about 1.4 prescriptions per resident, according to a report published online March 3 in the journal JAMA Internal Medicine.

A small but significant percentage of those residents appeared to be engaging in "doctor shopping," which indicates drug abuse and increases their risk of overdose death, said senior study author Dr. Timothy Jones, state epidemiologist for the Tennessee Department of Health.

Among patients who received narcotic pain killers in 2011, 7.6 percent got prescriptions from more than four doctors and 2.5 percent went to more than four pharmacies to get their medication. Nearly 3 percent had an average daily dose of more than 100 morphine milligram equivalents (MME), considered a high-risk dosage.

"There is a pretty substantial subgroup of Tennesseans who are using multiple doctors, multiple pharmacies and getting very high doses," Jones said.

A second new study appearing in the same journal found that having prescription narcotics around, even for legitimate purposes, helps fuel ongoing drug addiction.

Painkillers obtained from a friend or relative, either freely given or purchased, provide about half the prescription narcotics used by chronic abusers, according to the study by the U.S. Centers for Disease Control and Prevention.

"These drugs have risks, and sharing medications can share those risks and increase the risk that someone could overdose and die," said lead author Christopher Jones, now a senior adviser in the Office of Policy and Planning at the U.S. Food and Drug Administration.

In Tennessee, overdose deaths due to prescription drugs increased nearly fivefold during the past decade, Tim Jones said, rising from 118 deaths in 2001 to 564 in 2011. There now are more deaths related to narcotic painkillers than heroin and cocaine combined, he said.