Understanding facial expressions of pain in patients with depression

Abstract Although depression is associated with more clinical pain complaints, psychophysical data sometimes point to hypoalgesic alterations. Studying the more reflex-like facial expression of pain in patients with depression may offer a new perspective. Facial and psychophysical responses to non-painful and painful heat stimuli were studied in 23 patients with major depressive disorder (MDD) and 23 matched controls. As psychophysical data, pain thresholds, tolerance thresholds and self-report were assessed. Facial responses were videotaped and subjected offline to FACS (Facial Action Coding System) analysis. One of the key facial responses of pain, which is a known facial signal of negative affect (contraction of the eyebrows), was significantly increased in MDD patients. Moreover, facial expressions and pain ratings were strongly correlated in MDD patients, whereas these two response systems were - in line with established findings - only weakly related in healthy participants. Pain psychophysics was unaltered in MDD patients in comparison to healthy controls. In conclusion, the facial expression of pain in MDD patients indicates rather hyper- than hypoalgesia, with enhanced affective pain processing. Moreover, the linkage between subjective and facial responses was much stronger in MDD patients, which may be due to a reduced influence of social display rules, which normally complicate this relationship. Perspective The facial expression of pain in patients with depression indicates stronger affective pain processing and stronger association with self-report than in healthy individuals.