Enhanced central thermal nociception in mildly depressed nonpatients and transiently sad healthy subjects

Evidence of support for sensory changes during minor depression and sadness is scarce and the neural mechanisms are unclear. We assessed central pain processing engaged in nociceptive C-fiber polymodal activity by examining the perception of a non-noxious unpleasant burning sensation induced by a thermal grill illusion, in 26 nonpatients with minor depression (19 females) and 28 healthy subjects (18 females), between 19 and 61 years old and pain free at the study. Controls were also subjected to induction of transient moods. Subjects with depression reported increased pain perception; this increase was more pronounced for the affective dimension of pain (unpleasantness) than for its sensory dimension (intensity). The perception of pain unpleasantness, pain intensity, and overall pain showed positive and linear correlations with depression levels measured by Zung's and Beck's scales. In controls, sad mood induction only increased the scores assigned to negative mood-describing adjectives; the perception of pain intensity, unpleasantness, and overall pain were significantly increased following sad, but not neutral or elevated, mood inductions. Yet, pain intensity and unpleasantness were correlated linearly and reciprocally to positive, instead of negative, mood-describing adjective scores. Thus, there is a central thermal hyperalgesia in subjects with minor depression and sadness.

There is a central thermal hyperalgesia in subjects with minor depression, probably associated with an enhanced central processing of nociceptive C-fiber polymodal activity at anterior cingulate cortex, that is predominately expressed as an increased unpleasantness and that could be in part counteracted by behavioral therapies leading to mood elevation.