What Drives Affective Polarization? A Systematic Literature Review

This article synthesizes causal evidence on affective polarization through a systematic literature review spanning 2012–2025. Anchored in an emergence framework, we catalog 135 peer-reviewed studies located via Google Scholar and Scopus and retained using SCImago Journal Rank indexing (PRISMA-consistent). We code each article for outcome (vertical attitudes toward parties/elites vs. horizontal attitudes toward citizens), research design, measures, setting, and five driver families: psychological factors, media and information environment, identity and group processes, institutional factors, and socioeconomic factors. The corpus is highly U.S.-centric, but it also includes cross-national and diverse country cases. Horizontal and vertical outcomes are studied in comparable numbers, yet their joint dynamics are rarely examined. Observational surveys account for the majority of designs (65%), with experiments (22%), mixed designs (9%), and computational/other approaches (4%) less common. Explanations centered on psychology, media exposure/content, and identity processes dominate; institutional and socioeconomic mechanisms remain comparatively thin. Scholarly output rises sharply after 2020, particularly in areas related to psychological and media drivers, with recent growth in institutional accounts. We highlight research needs, including comparative designs that leverage variation in media and party systems, integrative analyses of horizontal-vertical interactions, more rigorous and comparable measurement, and longitudinal/panel studies to link short-run shocks with slow-moving trends.