Formation of professional social networks via physicians' online engagement: Evidence from Sina Weibo and Sina Health

The professional social networks of physicians are an essential source of health-related user-generated content and online social capital. Yet limited research has examined how social networks of physicians emerge at the level of relationships between physicians. To help fill this gap, this study investigates the formation of followship between physicians (i.e., when one physician follows another) from the perspectives of network structures, actor attributes, and external contextual factors. Using exponential random graph models and strategic network formation models, this study analyzes the effects of reciprocity and transitive closure, physicians' social media and online healthcare community (OHC) engagement, and physicians' interaction networks. The results reveal that physicians' professional social networks have a reciprocated and open structure. Physicians' social media connectivity and content, online service performance, professional capital, and social identity homophily facilitate the formation of professional social networks. In addition, the interaction networks have an entrainment effect on professional social networks. This study reveals the mechanism of social processes, including reciprocity, preferential attachment, and homophily, in the formation of social networks. The results also extend social cognitive theory and signaling theory into the context of physicians' professional social networks.