The potential role of cortisol as a biomarker of physiological interdependence in romantic couples: A systematic review

•Romantic partners may regulate one another’s physical and emotional states.•The literature lacks support for the mechanisms underlying this regulation role.•Cortisol may be a biomarker to measure interpersonal physiological contagion.•We propose physiological interdependence as an interpersonal homeostasis model. Significant evidence supports the link between relationships and health including the potential for interpartner regulation of intrapersonal physical and mental homeostasis. Physiological interdependence is proposed as a term to summarize the adaptive process in which partners demonstrate physiological contagion that evolves with repetition to create a new homeostatic state regulating individual physiological functioning. Through a systematic review consistent with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P), the present study reviewed the literature examining the interdependent role of diurnal cortisol with romantic couples. The literature search yielded thirteen articles that included statistical modeling testing interdependence between partners in a couple and at the individual level. Five themes emerged from the literature including cortisol synchrony, cortisol and health, cortisol and emotions, cortisol and internal relationship factors, and cortisol and factors external to the romantic relationship. Findings suggest a potential for romantic partners to regulate one another’s emotional and physiological states, but this process may not be present in both partners. More research is needed to substantiate a regulatory role as the current literature supports correlations.