Couched within the self-effects paradigm of social media influence, this research examines how posting a health promotion message to one’s social media influences one’s own, versus others’, later health behaviors, with emphasis on emotional intensity and message sharing directives. 382 participants viewed one of eight versions of a melanoma awareness video and were given the opportunity to post it to their Facebook page. Video sharers reported increased sun safety behavior one week later, even after accounting for a range of sun safety-related predictors. Emotional intensity and self-efficacy emerged as key message sharing predictors. These findings align with cognitive dissonance theory, offering unique evidence in a mediated context with relatively enduring effects, and expands the dialogue about the self-persuasive power of social media.

The rapid diffusion of social media has raised numerous questions regarding its influence in a wide range of contexts. Within health communication specifically, research has primarily examined how health messages are disseminated through social media and to what effect (see Grajales, Sheps, Ho, Novak-Lauscher, & Eysenbach, 2014, for a review). Although clearly important questions, such inquiries typically focus on the effect that health-related social media posts have on the message receiver. However, an intriguing alternative question is: what impact does posting health-related messages to social media outlets have on the behavior of the message poster themselves? Although the phenomenon of so-called “self-persuasion” is acknowledged in psychological processes of influence (e.g., dissonance theory; Festinger, 1957) and calls for greater investigation of such processes have emerged recently (Valkenburg, 2017), this phenomenon has not yet received close empirical testing within social media contexts. Yet, consider the following: at present there are an estimated 1.49 billion daily users and 2.27 billion monthly users of Facebook alone (fb.com, 2018). Further, among US users of social media, 36% share news stories sometimes or often (Mitchell, Gotfried, Barthel, & Shearer, 2016). Given the extensive diffusion of social media in the current environment and the relative frequent sharing of messages that takes place within that context, the potential for self-persuasion is profound. If it is indeed the case that social media posting can serve as a means of self-persuasion, understanding the features of messages that lead to message sharing is especially important. There is much evidence that message emotionality generates message diffusion (e.g., Berger & Milkman, 2012; Dunlop, Kashima, & Wakefield, 2010). What is as yet unknown, however, is the extent to which the explicitly cognitive route of asking people to share messages adds any additional value.