Longitudinal changes in spouses' HPA responses: Convergence in cortisol patterns during the early years of marriage.

Objective: Drawing on theories of bidirectional influence between relationship partners (Butler, 2011; Diamond & Aspinwall, 2003), the authors applied dyadic analytic methods to test convergence in cortisol patterns over time in newlywed couples.

Method: Previous studies of bidirectional influence in couples' cortisol levels (Liu, Rovine, Klein, & Almeida, 2013; Papp, Pendry, Simon, & Adam, 2013; Saxbe & Repetti, 2010) found significant covariation in couples' daily cortisol levels over several days, but no studies have tested whether cortisol response similarity increases over time using a longitudinal design. In the present study, 183 opposite sex couples (366 participants) engaged in a conflict discussion in a laboratory visit about 6 months after their marriage, and again about 2 years into the marriage. At each visit, spouses provided saliva samples that indexed cortisol levels before, during, and after the discussion. This multimeasure procedure enabled modeling of spouses' cortisol trajectories around the conflict discussion.

Results: Findings showed significant convergence in couples' cortisol trajectories across the early years of marriage; couples showed significantly greater similarity in cortisol trajectories around the conflict discussion as their relationship matured. Cohabitation length predicted stronger convergence in cortisol slopes prior to the conflict discussion. Couples' relationship dissatisfaction was associated with a greater degree of convergence in spouses' acute cortisol levels during the conflict discussion.

Conclusions: Findings suggest that spouses increasingly shape each other's cortisol responses as their relationship matures. Findings also indicated that increased similarity in acute cortisol levels during conflict may be associated with poorer relationship functioning.