ORIGINAL MANUSCRIPT Emotional competencies relate to co-rumination: Implications for emotion socialization within adolescent friendships Sarah K. Borowski 1 | Janice Zeman 2 1 University of Missouri 2 William and Mary Correspondence Sarah K. Borowski, Department of Psycho- logical Science, University of Missouri, 210 McAlester Hall, University of Missouri, Columbia, MO 65211. Email: sbch7@mail.missouri.edu Abstract Despite the acknowledged importance of friendships in emotional development during adolescence, little research has empirically examined emotion socialization processes within friendships. Co-rumination is one such process that may involve many emotion- related skills due to its negative emotional focus and links to emo- tional distress. The current study examines whether adolescent friends’ emotional competencies (i.e., emotional awareness, emotion regulation) relate to co-rumination. Adolescents (N 5 192; 53% girls; M age 5 12.67; 76% European American, 17.7% African American) par- ticipated with a reciprocated same-sex best friend. Adolescents reported on their own and their friends’ emotional competencies and participated in observed video-taped problem discussion task that was coded for co-rumination. Results indicated that indices of poor emotional competence related to greater co-rumination for girls. For boys, stronger emotional competence related to greater co- rumination. There were more significant links to co-rumination from adolescents’ perceptions of their friends’ emotion regulation than self- reports of their own emotion regulation. Results are discussed with a focus on implications for emotion socialization within the best friend context during early adolescence. KEYWORDS emotion regulation, emotion socialization, friendships 1 | INTRODUCTION Developing and maintaining close friendships is a central task of adolescence (Hartup, 1996; Rubin, Coplan, Chen, Buskirk, & Wojslawowicz, 2005) with critical implications for later psychosocial adaptation (Prinstein, 2007). An important but understudied aspect of close friendships is the expression and management of emotion within such relationships (Hubbard & Dearing, 2004; Klimes-Dougan et al., 2014) and processes through which friends might socialize emotional expressivity. At the core of one friendship process, co-rumination, is the discussion of negative Social Development. 2018;1–18. wileyonlinelibrary.com/journal/sode V C 2018 John Wiley & Sons Ltd | 1 Received: 31 July 2016 | Revised: 19 February 2018 | Accepted: 21 February 2018 DOI: 10.1111/sode.12293