Disentangling the longitudinal relationship between social media use,...

The reciprocal associations between social media use, political expression, and political participation are central to communication scholars. The cross-lagged panel model (CLPM) represents a common and widely advocated analytic approach to test these relationships. However, it fails to separate within- from between person effects. In this paper, we propose a random intercept cross-lagged panel model (RI-CLPM) disaggregating within-person and between-person effects. Using three-wave panel data, we demonstrate positive associations between social media use, political expression and online as well as offline participation consistently across waves using the CLPM. However, these relations could not be observed at the within-person effects level with the RI-CLPM. This suggests that the associations between social media use, political expression and political participation are mainly driven by trait-like differences and not by individual changes over time, fundamentally challenging some of the key conclusions of previous research. Implications for political communication scholarship are discussed.