Pain modulation by your partner: An experimental investigation from a social-affective perspective.

BACKGROUND: Social context such as the relationship between a person experiencing pain and a caregiver has been shown to affect the experience of pain, yet, results are not consistent. Possibly, differential effects of interpersonal relationships are modulated by affective states expressed by social partners. Viewing partner pictures in experimental designs is not only associated with lowered perceived pain intensity, but also affects neural responses. However, the role of affective modulation is not clear. The present study aimed to systematically examine the pain modulating effects of stimuli varying in affect and social content including personal relevance using subjective report and psychophysiological measures of facial and autonomic activity.

METHODS: Twenty-nine women underwent a tonic heat pain paradigm with simultaneous picture viewing to investigate the influence of their partners' faces with a neutral facial expression compared to strangers' happy, angry and neutral facial expressions on pain intensity and accompanying psychophysiological parameters (facial activity: corrugator muscle activity, autonomic activity: skin conductance level, heart rate). In addition to perceived partner support and relationship characteristics, the contribution of the affective value (valence, arousal) of the partner faces to the observed pain modulation was examined.

RESULTS: Partner and happy faces reduced self-reported pain intensity and corrugator activity, the latter being lowest when viewing partner faces as compared to all other picture categories. As corrugator activity is indexing stimulus unpleasantness and a core feature of the facial pain expression, this physiological pattern matches well with the subjective ratings. Neutral objects, neutral and angry faces had no effect on pain self-report, although angry faces were rated as highly negative. Partner faces also led to increased skin conductance, being an index of motivational activation, and heart rate deceleration, possibly reflecting increased sensory intake. Partner-related pain modulation was primarily related to perceived arousal of the partner's picture, i.e., the intensity of the activation of approach motivation, and pain-related catastrophizing.

DISCUSSION: Our results are partially consistent with emotional pain control models, especially regarding the modulatory influence of valence. Within the context of socially adaptive behavior, they particularly underline the social signal value of emotion and attachment figures. Clinically, our results imply that just looking at pictures of one's partner when undergoing acute painful procedures can have a robust hypoalgesic effect.