Humans are pair bonders who face costs when experiencing separation or isolation from close, trusted companions.  Another reason to find ways to increase relationship harmony is to forestall the adverse effects of isolation or separation.

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Sugarcoated isolation: evidence that social avoidance is linked to higher basal glucose levels and higher consumption of glucose

Association of loneliness with all-cause mortality: A meta-analysis

Loneliness and social isolation as risk factors for mortality: a meta-analytic review

Every Time You Go Away: Changes in Affect, Behavior, and Physiology Associated With Travel-Related Separations From Romantic Partners

The emotional cost of poor mating performance

Determinants of female sexual orgasms (more masturbation has not made women more orgasmic)

Between- and within-sex variation in hormonal responses to psychological stress in a large sample of college students

Loneliness as a specific risk factor for depressive symptoms: cross-sectional and longitudinal analyses

Depression-like behavior and stressor-induced neuroendocrine activation in female prairie voles exposed to chronic social isolation

Spouses’ Cortisol Associations and Moderators: Testing Physiological Synchrony and Connectedness in Everyday Life

Growing Desire or Growing Apart? Consequences of Personal Self-Expansion for Romantic Passion