OBJECTIVES - We examined whether anger-in, anger-out, and hostility predicted symptom-specific muscle tension reactivity during anger induction (but not sadness induction) among patients with chronic low back pain (CLBP). For patients with CLBP, relevant muscles are the lower paraspinals (LPs). Anger-in x hostility and anger-out x hostility interactions were tested to determine whether particularly reactive groups of patients could be identified with a multivariable profile approach.
METHODS - Ninety-four patients with CLBP underwent anger recall (ARI) and sadness recall (SRI) interviews, whereas LP and trapezius electromyography and systolic blood pressure, diastolic blood pressure, and heart rate were recorded. They completed anger-in, anger-out, hostility, and trait anger measures.
RESULTS - Hierarchical regressions were used to test anger-in x hostility and anger-out x hostility interactions for physiological changes during the ARI and SRI. A significant anger-in x hostility interaction was found for LP change during the ARI (but not SRI) such that high anger-in/high hostility patients evinced the greatest reactivity. Effects for trapezius reactivity were nonsignificant. Significant anger-in x hostility interactions were also found for systolic blood pressure and diastolic blood pressure changes during the ARI such that high anger-in/low hostility patients showed the smallest changes. The anger-out x hostility interaction for diastolic blood pressure change during ARI was also significant such that high anger-out/low hostility patients showed the smallest changes. All effects remained significant with trait anger controlled.
CONCLUSIONS - A multivariable profile approach may help identify especially vulnerable patient groups. Patients with CLBP who tend to suppress anger and are cynically hostile may be more likely to experience high levels of muscle tension near the site of pain and injury during anger, but not during sadness, than other groups.