Experimental pain sensitivity in subjects with major depression: Many pain complaints without hypersensitivity

Patients with major depression frequently complain of pain, but conflicting data exist concerning their changes in pain sensitivity. This study aimed at comparing the sensitivity to moderate controlled pain between subjects presenting a major depressive episode (isolated and recurrent depressive episodes or a bipolar disorder), controls, and subjects with schizophrenia from a previous study.

Pain sensitivity was assessed obtaining the visual analog scale (VAS) rating for the application of a 160 kPa pre-fixed pressure (fpVAS), the pressure corresponding to a VAS score of 3, and the time required to achieve a VAS score of 3 during ischemia induction. The effects of depression intensity, alexithymia, current and past general pain, and of six weeks of antidepressant treatment on fpVAS were investigated.

The results did not differ significantly between the depressed groups and the controls, without any effect of depression intensity. Presence of long-lasting pain and current pain felt on the day of testing correlated with fpVAS. The subjects of the depressed group were less sensitive than subjects with schizophrenia. FpVAS was significantly lower before and after antidepressant treatment in the subjects presenting clinical improvement.

No difference in experimental pain sensitivity and expression between major depressive episode subjects and controls, in opposite to pain complaints, is to be detected. The changes in the sensation of pain routinely attributed to subjects presenting depression may result from changes in a differential processing of pain signals, not in relation with the depression intensity, or the kind of depressive disorder.