By Pat Anson, Editor

Long term use of opioid pain medication raises the risk of developing depression, according to a large new study published in the Annals of Family Medicine.

Researchers at St. Louis University analyzed data from over 100,000 patients treated by the Veterans Health Administration and two private healthcare systems and found that about 10 percent of them developed depression after using opioids for more than 30 days.

All of the patients were new opioid users being treated for arthritis, back pain, headache, musculoskeletal pain or neuropathic pain, who had not been diagnosed with depression before starting opioid treatment.

"Findings were remarkably consistent across the three health care systems even though the systems have very different patient characteristics and demographics," said lead author Jeffrey Scherrer, PhD.

“In all three patient populations, longer duration of opioid analgesic use was associated with new-onset depression after controlling for pain and daily morphine equivalent doses.”

Scherrer believes the depression may be caused by changes in brain regions associated with reward and pleasure, as well as lower testosterone levels caused by opioids.  

“Patients and providers should be aware of all pros and cons before initiating a medication and our research supports discussing depression,” he said.  “In addition to common practice of screening for depression at initiation, our study supports repeated screening for depression during the course of opioid therapy. Certainly not all patients will develop depression. However new onset depression certainly complicates pain management, not to mention the burden of the disease itself. "

One of the co-authors of the study is Mark Sullivan, MD, who is a board member of Physicians for Responsible Opioid Prescribing (PROP), an advocacy group funded by Phoenix House, which operates a chain of addiction treatment centers.

“Certainly chronic pain is associated with depression. How much of a role opioids might contribute is I still think somewhat unclear. Our population is aging and not everything is amenable to surgery or injections. NSAIDs are not without risk especially in an older population,” wrote David Smith, MD, Children’s Hospital of Wisconsin, in a comment about the study on the Annals of Family Medicine website.

“There are not other good options for pain control. For example, tramadol is a weak opioid and has a number of side effects. There is a lot more that could be done with physical therapy and exercise but by themselves they are not sufficient in many cases. Although I think we need to address the misuse of narcotics, we need to be very careful not to throw out a very useful treatment for an aging population.”

One recent study found that about one in five patients with lower back pain suffer from depression.

Another study found that opioids are significantly less effective if a patient with low back pain suffers from depression or anxiety.