Pain sensitivity in chronic psychoemotional stress in humans.

Results were obtained from comparative studies of skin pain sensitivity (pain thresholds) using focused ultrasound in 51 healthy men and 101 patients with neurasthenia. Neurasthenia is a natural "model" of chronic psychoemotional stress, and patients showed a reduction in the pain threshold which was not accompanied by a reduction in the threshold of sensitivity to tactile stimulation. A reduction in the pain threshold, reflecting a weakening of central descending tonic inhibition, was probably due to a reduction in the activity of the brain's opioid system during long-term psychoemotional stress. Analysis of the relationships between the pain sensitivity threshold and pain syndromes suggests a role for changes in the nociception system in chronic psychoemotional stress, as part of the mechanism of pain formation.