Negative mood mediates the effect of poor sleep on pain among chronic pain patients.

OBJECTIVES: Sleep disturbances and increased negative mood are common among chronic pain patients. Research suggests that sleep disruption can contribute to increased pain; however, the role of negative mood in this relationship is unclear. The present study investigated the relationship among sleep disturbance, negative mood, and pain within a large sample of chronic pain patients. It was hypothesized that negative mood would mediate the relationship between sleep and pain.
METHODS: In all, 292 chronic pain patients (116 facial pain, 55 back pain, 121 fibromyalgia) between 18 and 65 years of age (M=46.67) were recruited from 3 chronic pain clinics at a large tertiary care hospital. Patients completed validated measures of pain, negative mood, and sleep during a routine clinical assessment. Structural equation modeling examined the relationship between sleep, negative mood, and pain.
RESULTS: All 3 groups of patients reported sleep disturbances, with these being highest among back pain and fibromyalgia patients. Structural equation modeling analyses revealed a significant direct relationship between poor sleep and pain, and further demonstrated that negative mood mediated the relationship between poor sleep and pain in this sample of chronic pain patients. DISCUSSION: These findings suggest that addressing negative mood directly, or by addressing sleep disturbances in chronic pain patients, may have a beneficial impact on patients' pain. As sleep disturbance may be causing negative mood, treating the sleep disturbance may also be beneficial among chronic pain patients. Negative mood may perpetuate the impact of sleep disturbances on pain, possibly through increased arousal or disruptions in diurnal patterns.