Pain threshold is reduced in depression.

Pain and depression may share common neurochemical substrates, therefore the study of pain sensation in depression might be valuable in the investigation of the pathophysiology of depression itself. In order to investigate the sensation of pain in depression, we measured pain threshold and sensory threshold by means of a dental tester, comparing a group of depressed patients with healthy volunteers. The results showed the presence of a higher sensory threshold and pain threshold in patients than in controls. This may be related to a hyperfunction of the opiate system, which in turn might be primary or secondary to a decreased modulatory function of other neurotransmitters, in particular of serotonin, whose abnormalities in depressive states are well-documented.