Chronic pain patients with depression three times more likely to receive opioid medications

University of WashingtonNov 16 2009

Chronic pain patients with a history of depression are three times more likely to receive long-term prescriptions for opioid medications like Vicodin compared to pain patients who do not suffer from depression, according to new research.

The study, published in the November-December issue of the journal General Hospital Psychiatry, analyzed the medical records of tens of thousands of patients enrolled in the Kaiser Permanente and Group Health plans between 1997 and 2005. Together, the insurers cover about 1 percent of the U.S. population. Long-term opioid use was defined as a patient receiving a prescription for 90 days or longer.

"It's very widespread," said Mark Sullivan, M.D., a study co-author and professor of psychiatry at the University of Washington. "It's a cause for concern because depressed patients are excluded from virtually all controlled trials of opioids as a high risk group [for addiction], so the database on which clinical practice rests doesn't include depressed patients."

Sullivan said most clinical trials exclude people with more than one disorder, but noted the problem is more worrisome here because depression affects so many — about 10 percent to 20 percent of the population.

The connection between pain and depression is complicated. First, no one really knows how often chronic pain and depression co-occur: 46 percent of patients seeing primary care doctors for ongoing pain have a history of depression and the vast majority of those seeing pain specialists have suffered both disorders, according to the authors.

"If you study depressed people, they tend to have lot of pain complaints that are poorly responsive to a lot of things so it's not surprising that they end up on opioids," Sullivan said.

Being depressed might make pain hurt more. "Emotional and physical pain aren't all that different," Sullivan added. "The same brain zones light up [in imaging studies]."

"Depression is mediated in some significant part by the brain's opioid receptor systems; these things run together at every level that you look at them," said Alex DeLuca, M.D., a consultant on pain and addiction and former chief of the Smithers Addiction Research and Treatment Center. He has no affiliation with the new study.

Consequently, it is impossible to tell whether pain is causing or exacerbating depression — or vice versa. To Sullivan, the bottom line is that "it is very important that opioid treatment for chronic pain does not replace or distract from treating mental disorders. 'Both' works better than 'either/or.'"