The number of people who've accidentally overdosed on prescription drugs has increased dramatically in the U.S. A new study looks at how Americans are getting their hands on these drugs and why one state in particular is seeing the largest increase. 

They're prescription narcotics you've most likely heard of. 

Aron Hall with Centers for Disease Control and Prevention says, “Some common brand names for these drugs include vicodin, percocet, as well as methadone or methadose." 

They're painkillers, often at the root of unintentional prescription drug overdose deaths. The number of these deaths has been on the rise, and researchers studied the trend by focusing on one particular state. 

Dr. Leonard Paulozzi with Centers for Disease Control and Prevention says, “We picked West Virginia because it had some of the highest rates of prescription drug overdose in the country, and it has seen a recent dramatic increase in those rates." 

The study looked at the accidental prescription drug overdose deaths in 2006 and found the highest rates among men ages 18 to 54. Many lived in the state's poorest counties and several had a history of substance abuse. And the study had two other findings. 

Hall says, "In our study we found that a majority of people who overdosed on prescription drugs did not have prescriptions for the drugs that killed them." 

Nearly two-thirds obtained drugs without a prescription. And others got drugs through what's called "doctor-shopping." 

Paulozzi says, "They had gone to multiple physicians---five or more in the past year---trying to get as many prescriptions for the drugs as they could." 

The researchers say it's critical to try to prevent the illegal, non-medical use of prescription painkillers. 

Hall says, "Our study emphasizes the importance of clinicians and pharmacists counseling their patients, not only about the risks of overdose to themselves, but the potential risk of overdose to other individuals with which they might share their medication." 

One surprising fact to mention about this study is that it's the first to link medical examiner records with the prescription records of the deceased.