While the link between chronic pain and opioid use disorder (OUD) isn’t new, exactly why the two are biologically associated is still being explored. In the first study of its kind, researchers at the Ohio State University (OSU) Wexner Medical Center and College of Medicine and University of Michigan Medical School partnered together to take a look at how central sensitization could provide clues explaining the link. These findings are published in the journal PAIN Reports.Chronic pain may lead to OUD, and people with both unrelenting pain and OUD have a much harder time quitting use than those with the disorder only. Finding answers about how the two are connected in the brain is important to understanding how to potentially curtail opioid addiction.Central sensitization is abnormal pain processing in the brain and spinal cord. People with central sensitization have spinal cords that are abnormally good at sending pain signals to the brain, and the brain has difficulty shutting these receptors off. As a result, those with central sensitization tend to have less pain tolerance than others and are more likely to report constant high-levels discomfort.

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The team enlisted the help of 141 study participants from OSU’s Wexner Medical Center’s addiction treatment center in Columbus, Ohio. They administered the American College of Rheumatology 2011 Fibromyalgia Survey Criteria electronically. Participants also responded to questions about “pain interference, quality of life and items regarding pain-beliefs and expectations of pain and addiction treatment.”  They measured quality of life across eight life domains: “general health, physical functioning, mental health, social functioning, vitality, bodily pain, role limitations due to physical health and role limitations due to emotional problems.”“Our study is the first to give patients with opioid use disorder a scale that measures central sensitization,” said O. Trent Hall, lead author of the study and an addiction medicine physician in OSU’s Department of Psychiatry and Behavioral Health. “Our study provides the first evidence of central sensitization underlying the chronic pain and OUD relationship and demonstrates a new tool for easily measuring central sensitization among individuals with opioid use disorder.”According to Hall, the team discovered that greater central sensitization was associated with a lower quality of life among patients with OUD.“Patients higher in central sensitization were more likely to report pain as a major reason for why their opioid addiction first began, as well as for putting off addiction treatment, continuing and increasing their use of opioids, and fear of pain causing OUD relapse in the future,” said senior author Daniel J. Clauw, M.D., director of the Chronic Pain and Fatigue Research Center at the University of Michigan.“It’s important to me to search for new ways to help,” Hall added. “But we can’t create better treatments for chronic pain and opioid use disorder without first understanding how the two relate. I did this study because I believed it might offer a new window into what is happening in the brains of patients needing help with pain and addiction. We hope to put in a grant with the OSU team within the next year to expand upon these findings since we feel that treating opioid use disorder in someone with chronic pain should be quite different than someone without pain.”

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Study provides first evidence of link between opioid use disorder, chronic painCentral sensitization in opioid use disorder: a novel application of the American College of Rheumatology Fibromyalgia Survey Criteria