Mediation of chronic pain and disability on opioid use disorder risk by pain management practices among adult Medicaid patients, 2016-2019

We estimated the extent to which different pain management practices, considered together as well as individually, mediated the relationship between chronic pain or physical disability and new-onset opioid use disorder (OUD) in a large cohort of adult Medicaid patients. Considering the plausibility of the assumptions required to identify different mediational estimands, we estimated natural indirect effects when considering mediation through the group of mediators together and estimated interventional indirect effects when considering mediation through each pain management practice individually. We estimated each effect using a nonparametric one-step estimator. The pain management variables we examined mediated all of the total effect of chronic pain on OUD risk and nearly half of the total effect of physical disability on OUD risk. High-dose, long-duration opioid prescribing and co-prescription of opioids with benzodiazepines, gabapentinoids, and muscle relaxants each contributed substantially to the increased risk of OUD due to chronic pain (contributing to 10-37% of the overall effect) and more moderately to the increased risk of OUD due to physical disability (contributing to 3-19% of the overall effect). Antidepressant or anti-inflammatory prescribing and physical therapy generally did not contribute to increased OUD risk, and, in some cases, even contributed to small reductions in risk.