A systematic review, published in the October 2012 issue of the journal Addiction, found that only 4.5% of people who are prescribed opioid painkillers for chronic pain develop a problem with addiction.
Study Design and Results
Researchers reviewed 17 studies, which involved a total of 88,235 patients. Most of the studies included adult patients with chronic non-cancer pain; two also included patients with cancer pain; only one included patients with a previous history of dependence. The prevalence of addiction ranged from 0 to 31% in the various studies, with an average of 4.5%.
It should be noted that one of the studies included in the review reported that 25% of the patients became addicted, however, the particular group of patients in that study already had a high rate of alcoholism and illegal drug use. If that study were omitted, the prevalence average would be even lower than 4.5%.
The researchers concluded, “The available evidence suggests that opioid analgesics for chronic pain conditions are not associated with a major risk for developing dependence.”
In their discussion of the review, the authors said, “The most impressive finding of the present review is the deficiency of good-quality studies. This seems to stand in contrast to the widespread concern of doctors and authorities relating to the prescription of opioids for pain management.” In other words (my interpretation), the current push to prescribe fewer opioids for chronic pain patients is not based on quality research showing a significant danger of addiction, but rather an assumption by authorities that because opioid addiction has increased, it must be due to misuse by chronic pain patients.
If anyone ever did a really thorough and high-quality study on the subject, I suspect they would find that most of the people who are addicted to opioids got into that situation because they obtained the drugs illegally, lied about having chronic pain in order to get opioids, or had a problem with addiction prior to being prescribed an opioid for pain.
Another fact that should be mentioned is that most, if not all, of the studies reviewed used the term “dependence” rather than, or in addition to, “addiction.” The review authors pointed out that the ICD-10 and the DSM-IV diagnostic codes used by doctors have very different definitions of dependence but the studies reviewed did not make it clear which definition they were using. The ICD-10 criteria for dependence is tolerance (needing higher doses to achieve the same level of pain relief), withdrawal symptoms when stopping the drug, and a physical craving for the drug. In addition to those criteria, the DSM-IV code also requires a loss of control and continued use of the drug despite knowledge of negative consequences.
Studies that used the ICD-10 definition would have many more patients who qualified as being dependent on opioids since most people who take opioids for an extended period of time will meet that criteria. Long-term use of opioids does result in physical dependence––just as does long-term use of antidepressants or blood pressure medications. It's the loss of control and continued use of the drug regardless of negative consequences that tips the scale into addiction. So if any of the studies reviewed used the ICD-10 definition of dependence, it is likely that 4.5% average reported is higher than the actual percentage of people with chronic pain who become addicted to opioids.