Differential predictors of self-reported pain and experimental pain tolerance among treated opioid addicts

Patients with opioid dependence suffer a high prevalence of chronic pain and demonstrate reduced tolerance to cold pain compared to controls. The factors that predict self-reported pain and experimental pain tolerance are relatively unexplored in this population. This cross-sectional study examined predictors of cold pain tolerance using the cold pressor test and pain interference measured with the Brief Pain Inventory in a sample of 41 opioid dependent adults treated with methadone or buprenorphine. Primary predictors of interest were pain catastrophizing (PCS), discomfort intolerance (DIS), depression (PHQ9) and post-traumatic stress (PCL-C). Additional covariates were age, gender, race, education, marital/partnered status, disability status, homelessness, smoking, duration of opioid agonist therapy (OAT), and use of methadone (versus buprenorphine). Multivariate linear regression models were tested for each outcome and predictor, adjusting for additional covariates that were found to be significant on univariate testing. Participants (n=41) had a mean age 44(SD±9) years, were 44% female, 30% non-white. The median duration on OAT was 2 years (IQR: 1-3); 22% were on methadone. Nearly all participants (93%) reported pain in the past month, and the majority (83%) reported chronic pain (>6 months). In regression models, DIS was the only significant predictor of cold tolerance (β=0.05, 95%CI: 0.01-0.08, p<0.01). In contrast, PCS and depression were both found to be significantly associated with pain interference (β=0.06; 95%CI: 0.002-0.12, p=0.04 and β=0.12; 95%CI: 0.005-0.24, p=0.04, respectively), and results for PTSD approached statistical significance (β=0.05, 95%CI: -0.005-0.10, p=0.08). In summary, pain catastrophizing and depression predicted pain interference, but not cold pain tolerance, in a sample of opioid addicts treated with methadone or buprenorphine. In contrast, self-reported pain sensitivity (DIS) was associated with cold pain tolerance, but not pain interference. These results suggest that among treated opioid dependent patients, pain experiences and experimental pain tolerance are distinct and shaped by different factors.