After years of reoccurring kidney stones and regular surgeries, Jared Hess became addicted to painkillers.
After a monthlong stay in the hospital and being prescribed the powerful painkiller Oxycontin, Hess continued to use the drug against his doctors' orders, surreptitiously obtaining pills.
Within a year of first being prescribed the painkiller, he found himself in rehab. He was just 19 years old.
"I was in college when it first became a real problem. I lost interest in school, stopped going to class, my relationships with friends and family deteriorated," Hess, now 24, told ABCNEWS.com.
"I was doing it every day and by myself. My life revolved around getting the drug and using it," he said.
Hess now works for the nonprofit Faces and Voices of Recovery, which advocates for substance abusers, who like Hess, often have a hard time getting insurance companies to pay for their treatment.
Hess embodies the two groups experts say are most susceptible to painkiller abuse — patients prescribed drugs who later become addicted, and young people who generally begin using the drugs recreationally and not for medical reasons.
An estimated 5.2 million people used prescription pain relievers in 2006 for nonmedical reasons, up from 4.7 million in 2005, according to the Department of Health and Human Services. That's more than twice the 2.4 million people the department estimates use cocaine nationwide.
According to statistics compiled by the Partnership for a Drug Free America, nearly one in five teens, or a staggering 4.5 million kids age 12-19, reportedly abused prescription medications to get high last year. Despite an overall downward trend in overall drug use among teenagers, painkiller abuse is up, according to a White House report released by President Bush last month.
What makes opioids — the class of common pain drugs like Oxycontin and Vicodin — effective pain relievers is also what makes them so highly addictive, said Fred Berger, medical director of the Scripps McDonald Center, the drug rehabilitation center at Scripps Memorial Hospital La Jolla, Calif.
"Opioids are chemicals that attach to certain receptors in the brain. … These drugs both prevent pain and stimulate the pleasure center in the brain. Those drugs that are the most effective in terms of attaching to those receptors give the most relief from pain as well as the most pleasure."
Berger described a wide range of people who become addicted to painkillers from "little old ladies who fractured a vertebra, are placed on meds and then can't come off them or don't want to," to "teenagers looking through their parents' medicine cabinets in order to get high."
The most common medical problem abusers who get hooked typically have is lower back pain, he said.
"These drugs serve a purpose and that's to deal with short-term pain. There are physicians who prescribe drugs chronically and after a while patients become habituated. Patients need more medicine to have an effect, but the pain doesn't get any better. They become dependent and if they try to stop withdrawal symptoms set in and the pain becomes more accentuated," he said.
Of those patients legitimately prescribed painkillers, people with addictive personalities or who have been addicted to other substances in the past are particularly prone to developing addictions, experts told ABC News.