Does a microbial-endocrine interplay shape love-associated emotions in humans? A hypothesis

Emerging evidence suggests that the human gut microbiome plays a regulatory role in the endocrine system, influencing hormone activity and potentially shaping the emotional and physiological dimensions of behaviors such as aggression and emotional states, including love. Here, we review the hypothesis that microbial-endocrine interactions shape love-associated emotions by modulating hormone levels and activity. While the division of love into discrete components such as lust, attraction, and attachment is somewhat artificial and may not fully capture the complexity of human experience, the associated emotions nevertheless correspond to well-characterized neuroendocrine processes. Psycho-endocrinological theory proposes that the complex and nonlinear interplay between testosterone, estradiol, and other hormones drives emotions associated with lust; serotonin and dopamine play a role in emotions linked to attraction; and oxytocin and vasopressin influence the modulation of attachment and social bonds. Microbial communities may influence emotions and relationship dynamics through effects on the hormonal pathways linked to love-associated emotions. While non-human animal studies suggest microbiota can impact social bonding, sexual preferences, and stress-related behaviors, direct evidence in humans remains limited. Investigating the evolutionary underpinnings of microbial-endocrine interactions could provide insights into how microbes influence emotions beyond love, including hate and aggression-with important societal implications. Indeed, understanding these mechanisms could have profound implications for human relationships, mental health, and even therapeutic interventions targeting the microbiota-gut-brain axis. Future research is needed to unravel the extent to which microbiomes contribute to the neurobiology of love (and other emotions) and whether manipulating microbial communities could modulate emotional and social behaviors.IMPORTANCELove is often considered an abstract emotion, but emerging science suggests that it may be shaped by the microscopic inhabitants of our bodies: microbes. This paper explores the intriguing hypothesis that microbes can influence the hormonal and neural systems linked to love-associated emotions-via the microbiota-gut-brain axis. Drawing on animal studies and early human microbiome and endocrine research, we highlight how microbes modulate neurohormones like oxytocin, dopamine, and testosterone, which play key roles in social bonding. By regulating these systems, microbes may also shape emotional and behavioral responses. This research opens new avenues for understanding not just the (micro)biology of love but also the potential for microbiome-targeted therapies to support relational well-being. By linking microbiome and emotion science, the article raises the important question of whether love is a phenomenon influenced by our resident symbionts, adding an intriguing and potentially impactful dimension to our understanding of human connection and behavior.