Linking symptom-specific physiological reactivity to pain severity in chronic low back pain patients: A test of mediation and moderation models

Symptom-specific reactivity to stress (lower paraspinal muscle reactivity) among chronic low back pain (CLBP) patients may exacerbate chronic pain. It was hypothesized that among CLBP patients (N = 107) only stress-induced lower paraspinal reactivity, and not reactivity in other indexes, would predict pain severity (PS), and that lower paraspinal reactivity would mediate or moderate links between depression and PS. Electromyogram readings from lower paraspinal and trapezius muscles, systolic and diastolic blood pressures, and heart rate were collected during mental arithmetic (MA) and an anger recall interview. The moderator hypothesis was supported: Only lower paraspinal reactivity during MA was related significantly to PS, but only among patients with high levels of depression. Thus, a profile of lower paraspinal hyperreactivity plus depressed affect may aggravate CLBP.