Effects of experimental pain on cortisol in patients with depression and patients with chronic back pain

Introduction: Neuroendocrine studies have suggested that irregularities of the hypothalamic–pituitary–adrenal axis (HPA) play a causal role in the development and course of depression and chronic pain: Hypercortisolism has been associated with depression, low cortisol levels have been observed in some patients with chronic pain. However, little is known about the effects of experimentally-induced acute pain on cortisol secretion in patients with depression and chronic pain. Methods: We examined twenty-one patients with a major depression, twenty patients with chronic back pain and thirty-two healthy subjects were examined in an experimental pain paradigm. Pain intensity was rated by the participants with a visual-analog-scale. Salivary cortisol was assessed when the painful heat stimulus was applied and 45 and 60 minutes after the stimulus. We repeated the examination after 8 and 90 days. Results: We found no increase of salivary cortisol levels in the three groups after painful heat stimuli. Patients with chronic pain had lower cortisol AUC values compared to healthy controls and depressed patients at all time points (all p-values < 0.01). However, cortisol secretion in depressed patients did not differ from controls. Conclusions: Experimental heat pain stimuli did not elicit a significant cortisol response. The results confirmed the hypothesis that chronic pain is associated with hypocortisolism.