Presence of a friend is associated with progesterone response after social exclusion.

Social exclusion is a common form of indirect aggression and carries significant social and health costs. Close friendships may protect against exclusion and shape physiological responses. While oxytocin and cortisol have received substantial attention in this context, progesterone is also implicated in affiliative motivation and may be sensitive to social threat. The present study examined progesterone responses to social exclusion and subsequent reunion with a close friend. Female participants (N = 31) provided salivary progesterone samples at baseline, following exclusion (Yale Interpersonal Stressor; YIPS), and after reunion with a friend. During reunion, participants either received active support from their friend (venting), passive support (friend present but no discussion), or no support (alone). Results indicated a significant increase in progesterone from baseline to post-exclusion, which remained elevated at reunion. Trajectories also varied significantly: passive support sustained progesterone across phases, active support produced only a transient boost, and no support was associated with flat responses.