The autonomic reactivity of social exclusion in patients with psoriasis: a thermal imaging study

While emotion regulation seems to be well understood in the individual domain, information about the inherent link between emotion regulation and social contexts is lacking. In this study, we investigated the behavioral and physiological consequences of social exclusion in control participants (N=17) and in patients (N=17) with psoriasis, a skin disease known to be often accompanied with emotion regulation deficits. Firstly, participants faced the social induction phase by playing the Cyberball Game in which they were excluded or included by other players. Then participants played the Trust Game (TG) in the role of investor. All participants took part in both exclusion and inclusion social inductions and played the TG twice. In the TG, the investor has to decide how much of €10 to invest on familiar and unfamiliar players. The familiar (bad vs good) players were the same players previously encountered in the Cyberball Game. Participants' face temperature (peri-orbital region) during the task was measured by means of functional infrared thermal imaging (fITI). Face temperature in this area is known to reflect the activation of the sympathetic system. We tested whether social inclusion vs. exclusion affected participants’ trust toward other players by entering mean investments into a mixed Repeated Measures ANOVA with Group (patients vs controls) and Block Order (exclusion-inclusion vs inclusion-exclusion) as a between factors and Social Modulation (exclusion vs. inclusion) and Player (familiar vs. unfamiliar) as within factors. We found a statistically significant social modulation x player interaction. Newman-Keuls post hoc test showed that unfamiliar players were trusted significantly more after social exclusion, respect than social inclusion. In order to have a measure of the activation of the sympathetic system during the social modulation phase, we run a mixed repeated measures ANOVA with Group (patients vs controls) and Block Order (exclusion-inclusion vs inclusion-exclusion) as between factors and Social Modulation (exclusion vs. inclusion), Block Phase (start vs. end) and Periorbital Area (left vs. right) as within factors, on the temperature of the peri-orbital regions. We found a significant Group x Social induction interaction, showing that while controls had a lower temperature during inclusion with respect to exclusion, patients’ temperature during social inclusion was as high as the one recorded during social exclusion. Morever, during the social inclusion phase, patients’ periorbital temperature was higher respect to controls’ one. Taken together, these results seem to suggest that for patients, social inclusion was as stressful as exclusion. In line with this physiological result, we found that while controls reported to be much happier after social inclusion than exclusion, patients’ emotional state seemed not to be enhanced by being included. Finally, we found that higher temperature during social exclusion predicted higher trust investments towards unfamiliar opponents in patients but not in controls. This result suggests that patients might have difficulties in regulate the sympathetic activation experienced during painful social interactions and to adjust future behavior consequently. Together our results highlight two important features of autonomic reactivity in psoriasis patients who have a deficit in emotion regulation (i.e. lack of emotional clarity): on the one hand, their sympathetic system does not seem to be relieved during social inclusion, on the other hand the sympathetic activation during social exclusion seems to influence subsequent social behavior more than in controls.