Adolescent girls' intrapersonal and interpersonal parasympathetic regulation during peer support is moderated by trait and state co-rumination.

Effective emotion regulation (ER) is integral to adolescents' mental well-being and socioemotional development. During adolescence, peer interactions have an increasingly salient influence on the development of effective ER, but not all supportive peer interactions support adaptive ER. Co-rumination reflects the tendency to seek ER support by engaging with peers in negatively focused discussion of ongoing problems. We examined associations between co-rumination (state and trait) with measures of individual's autonomic (i.e., respiratory sinus arrhythmia, RSA) and affective regulation (self-report) among 30 female close-friend dyads (ages 11-17; 74% White) while engaged in a support-seeking discussion in the laboratory. We found that trait co-rumination corresponded with RSA withdrawal during peer support, suggesting a potential mechanism by which co-rumination contributes to dysregulated ER. We also examined dyadic patterns of physiological regulation via prospective change actor partner interdependence models (APIM). Partner effects were moderated by behaviorally coded state co-rumination. Dyads with high state co-rumination displayed coupled RSA movement in opposite directions, while dyads with low state co-rumination exhibited coupled RSA movement in the same direction. These findings are consistent with similar physiologic linkages in close relationships observed in other developmental periods. Results highlight the importance of multimodal assessment for characterizing social ER processes across development.