The hormone best known for its role in inducing labor may influence our ability to bond with others

In a preliminary study, the hormone oxytocin was shown to be associated with the ability to maintain healthy interpersonal relationships and healthy psychological boundaries with other people.

This is one of the first researches into the biological basis for human attachment and bonding. One study indicated that oxytocin may be mediating emotional experiences in close relationships.

General knowledge has been established of the important role oxytocin plays in the reproductive life of mammals. The hormone facilitates nest building and pup retrieval in rats, acceptance of offspring in sheep, and the formation of adult pair-bonds in prairie voles. In humans, oxytocin stimulates milk ejection during lactation, uterine contraction during birth, and is released during orgasm in both men and women.

Inhaling oxytocin can have strong influences

Men who inhale a nasal spray spiked with oxytocin give more money to partners in a risky investment game than do men who sniff a spray containing no active ingredient, say economist Ernst Fehr of the University of Zurich and his colleagues.

Previous studies of nonhuman animals had suggested that oxytocin in the brain encourages long-term mating in pairs of adults and nurturing behaviors by mothers toward their offspring. This substance, which works as both a hormone and a neurotransmitter, fosters the trust needed for friendship, love, families, economic transactions, and political networks, Fehr proposes.

"Oxytocin specifically affects an individual's willingness to accept social risks arising through interpersonal interactions," he and his colleagues conclude in the June 2, 2005, of Nature magazine.

Scientists studied oxytocin's influence on male college students playing an investment game.

The oxytocin influence is "a remarkable finding," says neuroscientist Antonio Damasio of the University of Iowa College of Medicine in Iowa City in an editorial published with the new report. Damasio had previously argued that the hormone acts somewhat as a love potion. "It adds trust to the mix, for there is no love without trust," he says.

Worries may arise that crowds of people will be sprayed with oxytocin at political rallies or other events to induce trust in speakers, Damasio notes. However, he proposes that slick marketing strategies for political and other products probably already trigger oxytocin release in many consumers.

Fehr's group plans to determine what brain networks participate in oxytocin-inspired trust decisions and to consider whether oxytocin might counter social phobia and other mental disorders that result in social avoidance.

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