Oxytocin is produced naturally in the body and acts both as a hormone and as a neurotransmitter. It is involved in childbirth and breastfeeding, but it also influences brain systems involved in social evaluation, emotional salience and interpersonal behavior. In 2005, a team led by University of Zurich economist Ernst Fehr reported in Nature that intranasally administered oxytocin increased trusting decisions in a laboratory investment game. That result attracted widespread attention, yet later experiments produced mixed outcomes, with some studies replicating the effect and others finding no general increase in trust.

The uncertainty was amplified by methodological differences across the field. Many earlier experiments included relatively small samples, used different versions of trust tasks or measured psychological traits in inconsistent ways. Researchers also faced concerns about hypotheses being formulated after results were observed, a practice that can make apparently striking findings less reliable. Against this background, Fehr and colleagues designed a study with a larger sample and a hypothesis specified in advance: oxytocin would selectively increase trust among men with a low dispositional tendency to trust.

The international research team recruited 359 men who had first completed a questionnaire measuring their general disposition to trust. Participants identified as having relatively low trust scores were then randomly assigned to receive either oxytocin or an inactive placebo through the nose. Intranasal delivery is commonly used in laboratory studies because it is intended to allow the compound to reach the brain without the need for an injection, although the precise pathways and central effects of this method remain an active area of scientific debate. Neither the participants nor the researchers conducting the behavioral testing knew which treatment each man had received.

After treatment, the men played an anonymous trust game involving real money. Each participant began with an endowment of 12 euros and was placed in the role of an investor. He could transfer 0, 4, 8 or 12 euros to an unknown counterpart. The transferred amount was tripled, after which the trustee could return any amount. The investor’s decision therefore involved a calculated risk: transferring more money created a greater potential return, but also increased the amount that could be kept by the other player. In this setting, the amount sent serves as a behavioral measure of trust rather than a simple verbal statement of confidence.

Men in the low-trust group who received oxytocin transferred approximately 15 percent more money than comparable men who received the placebo. To strengthen the analysis, the researchers combined their results with data from an earlier comparable experiment, creating a pooled sample of 578 men with low dispositional trust. Across the combined dataset, oxytocin was associated with an increase of nearly 17 percent in trusting behavior. The relationship remained after the researchers statistically controlled for different personality characteristics, indicating that the result was not easily explained by broad differences in traits such as sociability or risk tolerance.

The effect was not observed as a universal shift toward trust. Within the selected low-trust group, men with the very lowest scores did not respond more strongly than men whose scores were somewhat higher but still fell within the low-trust range. This pattern suggests that oxytocin may act less like a general “trust drug” and more like a context-sensitive regulator of social expectations. Its influence may become visible when an individual begins with skepticism or caution, while producing little measurable change in people who are already relatively trusting.

The biological explanation remains unresolved. One possibility is that oxytocin increases the expectation that another person will cooperate, making a risky transfer appear more worthwhile. Another is that it reduces the perceived threat of betrayal or softens the emotional cost associated with being cheated. These possibilities are not interchangeable: raising expectations about cooperation would directly alter judgments about another person’s likely behavior, whereas reducing fear could change the emotional weight of the same risk without changing the underlying prediction. The study measured decisions, not brain activity or hormone signaling, so it cannot determine which mechanism is responsible.

The researchers deliberately restricted the experiment to men to make its results more directly comparable with previous oxytocin studies. That choice also leaves an important question unanswered: whether the same selective effect occurs in women. Future experiments will need to examine sex differences, individual personality profiles, dosage, social context and the reliability of intranasal oxytocin’s effects across laboratories. For now, the study offers a more precise message than the familiar claim that oxytocin makes people trust more. In men who are naturally reluctant to trust, the hormone appears capable of shifting behavior toward greater confidence in an anonymous partner—but its power is selective, conditional and rooted in a social decision rather than a simple chemical switch.

Subject of Research: People

Article Title: Oxytocin increases trust in men low in dispositional trust.

News Publication Date: 11 August 2026

Web References: https://doi.org/10.1073/pnas.2602655123

References: Bodo Vogt, Paul Bengart, Carolyn Declerck and Ernst Fehr. “Oxytocin increases trust in men low in dispositional trust.” Proceedings of the National Academy of Sciences, 11 August 2026. DOI: 10.1073/pnas.2602655123.

Keywords: Oxytocin, trust, behavioral economics, social behavior, neuroscience, hormones, randomized controlled trial, intranasal oxytocin, human behavior, decision-making

At the core of the study lies the intricate interplay between cortisol, a glucocorticoid hormone pivotal in stress responses, and oxytocin, a neuropeptide known for its role in social bonding and emotional regulation. Cortisol is well-documented for its immunosuppressive effects, often exacerbating inflammation and delaying tissue regeneration. Conversely, oxytocin not only fosters affiliative behaviors but also exhibits anti-inflammatory properties that may potentiate tissue repair. The current research leverages these established biochemical pathways to explore how physical intimacy may biochemically translate into tangible health benefits.

The experimental design involved controlled administration of oxytocin via intranasal routes alongside monitored episodes of intimate physical contact among subjects. By measuring salivary cortisol pre- and post-interventions, alongside quantifiable markers of wound healing such as re-epithelialization rates and inflammatory cytokine profiles, the investigators could elucidate the physiological underpinnings of social touch. The results demonstrated a marked reduction in cortisol levels coinciding with enhanced wound closure rates, underscoring the dual modulatory role of social interaction and hormone therapy.

This research builds upon a burgeoning body of literature contextualizing social connectedness as an integral determinant of physical health. Prior studies have linked social isolation and stress-induced hypercortisolemia to an array of chronic conditions, ranging from cardiovascular disease to impaired immune surveillance. By clearly delineating the biochemical effects of tactile intimacy, the study offers mechanistic validation to psychosomatic theories and opens pathways for novel clinical interventions.

The implications for clinical practice are multifaceted. Integrating relationship-based therapies and neurohormonal modulation could revolutionize strategies for managing inflammatory and stress-related disorders. For instance, fostering supportive interpersonal environments coupled with targeted oxytocin analogs may enhance recovery rates post-surgery or during chronic wound management. Such an approach transcends traditional pharmacotherapies by incorporating psychobiological dimensions of care.

Moreover, the study prompts a deeper inquiry into the contextual and dose-dependent effects of oxytocin and physical contact. Not all social touch engenders beneficial outcomes; factors such as relationship quality, individual psychological state, and oxytocin receptor sensitivity may modulate therapeutic efficacy. This nuanced understanding necessitates personalized protocols to optimize health outcomes through social and hormonal interventions.

From a neurobiological standpoint, the study illuminates the role of the hypothalamic-pituitary-adrenal (HPA) axis in mediating stress and healing responses. Physical touch appears to attenuate HPA axis hyperactivity, thereby lowering cortisol secretion. Concurrently, oxytocin may exert feed-forward effects by enhancing parasympathetic activity, promoting homeostasis and tissue regeneration. The dual modulation effectively creates a biochemical milieu conducive to accelerated healing.

The research methodology underscored rigorous controls to isolate the effects of social touch and oxytocin from confounding variables such as baseline health status, psychological stress, and environmental factors. Advanced biomarker assays quantified cortisol dynamics and pro-healing cytokine fluctuations, while precise wound measurement techniques provided objective endpoints. This methodological robustness strengthens the credibility and reproducibility of the findings.

Intriguingly, the study also gestures toward the potential evolutionary advantages of social bonding in promoting survival. The facilitation of wound healing via social mechanisms could have conferred adaptive benefits by reducing morbidity and infection risk in cooperative species. As such, the integration of endocrinology and social behavior research may redefine our grasp of human physiology and its evolutionary trajectory.

While the study’s findings are promising, the authors emphasize the necessity of further research to disentangle complex individual differences and explore long-term clinical applications. Investigations into genetic polymorphisms affecting oxytocin receptors, longitudinal studies of social behavior interventions, and translational research in diverse patient populations are pivotal next steps.

The innovative fusion of endocrinology, psychotherapy, and immunology manifested in this study heralds a new era of biopsychosocial medicine. By elucidating concrete biochemical pathways whereby social intimacy translates into health benefits, the research invites a reimagining of therapeutic approaches that honor the interconnectedness of mind, body, and relationships.

Corresponding authors Beate Ditzen, PhD, and Ekaterina Schneider, PhD, underscore the transformative potential of merging neurohormonal science with social dynamics. Their work not only advances academic understanding but also charts practical courses for enhancing human health and resilience through scientifically grounded, compassion-centered interventions.

As the global scientific community continues to unravel the mysteries of the human genome and brain, studies such as this highlight the indispensable role of social factors in shaping physiological outcomes. The elucidation of cortisol attenuation and oxytocin facilitation by physical intimacy situates social bonding as a potent, biologically embedded therapeutic tool with broad implications for medicine and public health.

This seminal research will be presented at the upcoming 2025 Congress of the German Society of Neurology (DGN), catalyzing dialogues among neuroscientists, endocrinologists, psychologists, and clinicians worldwide. The study stands poised to inspire integrative innovations that harmonize relational dynamics with molecular science, ultimately advancing holistic models of health care.

Subject of Research:
Oxytocin and cortisol modulation by intimate physical contact and its effects on wound healing.

Article Title:
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News Publication Date:
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Web References:
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References:
DOI: 10.1001/jamapsychiatry.2025.3705

Image Credits:
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Keywords:
Oxytocin, cortisol, wound healing, stress responses, neurohormonal modulation, endocrine system, human health, stressors, hormones, psychiatry, dermatology, neurology