Oxytocin raises trust in men who start with little

Clinical takeaway: Treat over-the-counter oxytocin claims skeptically. Twenty years of research supports a narrow effect on a lab measure of trust in low-trusting men, with nothing yet on symptoms, relationships, or function. 

Patients may arrive having already decided what oxytocin can do for them. Nasal sprays are marketed as a trust hormone, cuddle hormone, or bonding support. They often promise something specific: that a few drops will make connection easier, conversations warmer, other people less threatening. It is one of the few supplement categories where the pitch is about boosting relationships. 

Setting aside that supplements are unregulated, it's also not clear that oxytocin actually lives up to that hype. A 2005 trial first put the hormone's effect on trust into the scientific literature. The studies that followed split, some finding an effect and some finding none, but most of them too small to settle anything. The latest study is a randomized trial of intranasal oxytocin in men low in dispositional trust. 

Men given oxytocin entrusted about 15% more money to an anonymous counterpart than men given placebo. The separation held in models with and without controls for personality traits. Pooling with a comparable earlier sample added 219 men to the trial's 359 and put the increase at nearly 17%. Within that low-trust band, how low a man scored made no difference: the effect on the lowest scorers was no stronger than on men who scored somewhat higher but still qualified as low. 

Those screened as low in dispositional trust were randomized to a single intranasal dose of oxytocin or placebo, then played one round of an anonymous trust game for real money against an unseen stranger. The amount they sent was the trust measure. The hypothesis was preregistered, the step most of the earlier literature skipped. 

"After more than 20 years, we have now succeeded in providing robust evidence of a selective effect of oxytocin," says Ernst Fehr, PhD, professor of economics at the University of Zurich and senior author. 

Why the effect works this way is unresolved; the trial did not test biological mechanisms. "It's possible that the hormone intensifies the expectation that others will cooperate," Fehr added.

Source: Vogt B, et al. (2026 Aug 11) Proc Natl Acad Sci U S A. Oxytocin increases trust in men low in dispositional trust