Although previous research has linked depression with opioid use, the new study shows that increasing opioid drugs is directly linked to an increase in depression.
“Better understanding of temporal relationship between opioids and depression and the dose of opioids that places patients at risk for depression may inform prescribing and pain management and improve outcomes for patients with chronic, non-cancer pain,” said Jeffrey Scherrer, Ph.D., associate professor for family and community medicine at Saint Louis University, and his colleagues.
For the study, researchers evaluated questionnaires from 355 patients with chronic low back pain at their one-year and two-year follow ups. The participants were 72.4 percent female, older than 46 (75.2 percent) and mostly of Hispanic or African-American descent (57.5 percent). The patients reported the number of years they had been experiencing chronic pain.
Contributing factors for new-onset depression, according to this study and previous research conducted by Scherrer, may include both the amount of daily morphine exposure and the length of exposure. Further studies are needed to determine whether patients are at-risk due to past episodes of depression or recent depressive symptoms.
Scherrer noted that since the acceptance of the paper his team has continued to analyze a large Veterans Administration medical record database. They found that depression is usually connected to how long a patient has been taking opioid medications.
“After the paper was accepted at [the journal] Pain, we have been conducting ongoing additional analysis, with the support of National Institute of Health funding of a large VA patient database to determine if duration of opioid use and dose of opioid interact or have an additive effect on risk of depression,” Scherrer said.
“Our results support the conclusion that most of the risk of depression is driven by the duration of use and not the dose.
“Thus, a strong potential explanation of our finding that increasing opioid dose increases risk of depression could be that the patients who increase dose were the longer-using patients. This is logical as longer use is associated with tolerance and a need to increase opioids to achieve pain relief.”
“We hope to find risk factors such as opioid misuse that could be in the pathway from chronic opioid use to new onset depression,” Scherrer said. “This would expand the targets for intervention to limit the risk of depression in patients who need long-term opioid therapy.”
The study is published in the journal Pain.