| Individuals with chronic low back pain (CLBP) tend to develop pain-related anxiety, which is associated with problems such as continued pain, activity avoidance, depression, and reliance upon opiate analgesic medications. Multidisciplinary pain treatment centers are most successful in treating individuals with CLBP; however, mechanisms by which they are effective are not well understood. We tested two hypotheses using 185 CLBP patients who completed such a treatment program. We first predicted that correlations would be significant between change in each of the following variables: pain-related anxiety, physical activity level, pain, depressive symptoms, and opiate analgesic medication use. Second, we predicted that change in physical activity would mediate the relationships between change in pain-related anxiety and change in (a) pain, (b) depressive symptoms, and (c) opiate analgesic medication use. Using residualized change scores and structural equation modeling, we examined the significance of direct and indirect effects. Participants ranged from 24 to 71-years-old (M = 43.8, SD = 9.8), 67% of the participants were male, and they were primarily Caucasian (87.0%). Results largely supported our hypotheses. Change indicators for all variables were significantly correlated with the exception of the relationship between change in opiate analgesic medication use and physical activity, and the relationship between change in opiate analgesic medication use and pain. Additionally, change in physical activity partially mediated the relationships between change in pain-related anxiety and change in both pain (β = .043; 95% CI = .018 to .082, p = .001) and depressive symptoms (β = .023; 95% CI = .002 to .063, p = .027). When only significant paths were retained, the final model indicated good to superior fit (χ2 = 2.361, df = 3, p = 0.501; GFI = .995, CFI = 1.0, RMSEA = 0.0). Findings suggest that change in pain-related anxiety is related to change in important outcome variables such as pain and depression because patients are able to increase physical activity throughout treatment. This has implications for the structure of multidisciplinary pain treatment programs and suggests that changing physical activity is a primary mechanism for improving pain and depression in CLBP patients with pain-related anxiety. |
