We know how opioid addictions end: all too often, in death by overdose. About 16,000 Americans every year die of an overdose of opioid painkillers, such as oxycodone or fentanyl, according to the Centers for Disease Control and Prevention.
We know less about how opioid addictions start. It's much harder to find and study people who start taking too many pills than it is to count dead bodies. But it's becoming clear that the opioid addictions, which have ruined millions of lives over the past decade, rarely begin the way you might imagine a life-ruining addiction begins -- on some gang-ridden street corner.
Many start with an innocuous visit to the doctor's office.
To begin to figure out how many, a team at the Mayo Clinic, led by pain specialist Dr. W. Michael Hooten, analyzed the medical records of 293 patients given a short-term prescription for opiates for the first time in 2009. These patients were being treated for acute pain -- from traumas such as sprained ankles or major surgeries -- so their doctors did not expect them to become long-term users of painkillers.
Yet just over 1 in 4 of these patients went on to use opioid painkillers for longer than 90 days, researchers found. A quarter of this subset engaged in so-called long-term use, defined as receiving at least 120 days' worth of pills or more than 10 separate prescriptions.
It's not yet clear how many of these patients developed an opioid addiction, Hooten said. (He's planning on conducting further research in an effort to find out.) Past research has indicated that the "long-term" use category seems to be a key threshold for dependence: a large share of patients who take more than 120 days' worth of opioids for longer than 90 days are still taking them a year later.
"This study looked at behavior in 2009. If you went back and found the people who were long-term users then, I can guarantee you that many of them became addicted," said Dr. Andrew Kolodny, an expert in opioid addiction who was not involved in the study. "And I would not be surprised if some of them wound up dying of opioid overdoses."
The other key finding of the study was that patients who used painkillers for at least 90 days were much more likely than the rest to have issues with other types of addiction. About 37 percent of smokers in the study used painkillers for at least 90 days, compared to 20 percent of non-smokers, and 51 percent of those with a history of substance abuse did, compared with 24 percent of those with no history.
"The patients' age, their sex and even the severity of their medical problems are as not good predictors of short- or long-term use as a history tobacco use or of substance abuse," Hooten said.
This correlation indirectly supports the idea that the transition to long-term use was an addictive-type behavior, Hoten said. It also suggests that doctors should be especially cautious when prescribing opioid painkillers to patients with a history of substance abuse or smoking.
"Before you provide an opioid prescription to a patient, it's important to recognize that if they have a tendency to abuse substances, you should have a heightened sense of vigilance," Hooten said.
Doctors and governmental agencies have already take steps to cut down on abuse of opioid painkillers -- in part because it's become increasingly clear that the drugs are not very effective for treating chronic pain.
"They don't work well when you take them long term. They can even make pain worse," Kolodny explained.
Several states require that doctors check an electronic prescription database to see whether patients are receiving opioid painkiller prescriptions from other doctors before writing a prescription for the drugs.
But the efficacy of such measures is limited because those with drug addictions who get cut off by their doctor often seek out other sources of painkillers. They can buy or steal them friends and family or purchase them from a drug dealer or off the Internet. A tragically large share of them also switch to heroin, abuse of which has almost doubled since 2002.
For that reason, Kolodny said, it's crucial that doctors think carefully about whether to prescribe an opioid painkiller in the first place -- and that patients think carefully about whether to begin treatment with those drugs, especially if they have a history of addiction.
That's not to say that doctors should never prescribe opioid painkillers.
"These are extremely important medicines for end-of-life care," Kolodny said. "I think they play a very important role when used short-term -- for a few days after major surgery or a serious accident, for example. But using them long-term is a very bad idea."