Relationship Between Decreased Cortisol and Development of Chronic Pain in Traumatically Injured.

BACKGROUND: The relationship between pain and stress is widely accepted, yet the underlying neuroendocrine mechanisms are poorly understood. Cortisol secretion during a stress response, may distract attention from a painful stimulus, inhibiting pain. However, when pain is the stressor, cortisol secretion may intensify the pain experience and condition a fear-based memory of pain. This study attempts to determine the relationship between acute pain, chronic pain, and cortisol in the traumatically injured population. METHODS: Secondary analyses of a prospective observational study with participants from a Midwestern Adult Level I Trauma Center post traumatic injury, with interview and serum cortisol taken at hospitalization (baseline) and 6 mo after discharge, was completed using Ward's Method hierarchical cluster analysis, Pearson's correlations, and linear regressions. RESULTS: Two major clusters were identified. The Chronic Pain group were those who had severe pain at discharge and continued to have severe pain as defined by Numeric Pain Score. The Resolved Pain group were those who had moderate pain at discharge and their pain improved or resolved. Pain score at discharge significantly, negatively correlated with baseline cortisol levels (r = -0.142, P = 0.02). Minority status, single individuals, low cortisol at baseline, and greater psychological distress at baseline significantly increased the likelihood of developing chronic pain. CONCLUSIONS: Low cortisol and greater psychological stress, which are also associated with minority status and single individuals, contribute to chronic pain in the traumatically injured population. Trauma victims without an adequate cortisol response to acute injury and pain are at risk for development of chronic pain after injury.