Investigators from Saint Louis University analyzed medical record data of about 50,000 veterans who had no history of opioid use or depression, and were subsequently prescribed opioid painkillers.
As reported in the Journal of General Internal Medicine, patients who started and remained on opioids for 180 days or longer were at a 53 percent increased risk of developing a new episode of depression.
“These findings suggest that the longer one is exposed to opioid analgesics, the greater is their risk of developing depression,” said Jeffrey Scherrer, Ph.D., principal investigator of the study. “Opioids have long been known to allay pain and suffering, but reports of adverse effects are abundant and continue to emerge.”
Scherrer said even though there is no clear evidence about the mechanisms by which opioids may contribute to the development of depression in a patient, there could be several factors that lead to it.
Some of these include opioid-induced resetting of the brain’s “reward pathway” to a higher level, which means the chronic use of painkillers can elevate the threshold for a person’s ability to experience pleasure from natural rewards such as a food or sexual activity.
Other factors may include body aches months and years after the use of opioids has stopped, or other side effects such as adrenal, testosterone and vitamin D deficiencies and glucose dysregulation.
The study also suggests that the higher the dose of opioid analgesics, the greater the risk of depression.
“Preliminary evidence suggests that if you can keep your daily dose low, you may be at lower risk for depression,” he said.
Scherrer notes that even though a minority of patients take these medications chronically, they are at risk of developing depression that can affect their quality of life and ability to cope with chronic pain.
He noted that recent studies indicate that the use of prescription opioid analgesics has quintupled recently and that more than 200 million prescriptions were issued to patients in 2009 in the US.
“Even though the risk is not huge, there is enough exposure that we may have a public health problem,” he said.
Source: Saint Louis University