Links between oxytocin and increased feelings of trust and empathy have been documented for some time, leading many to speculate that the ‘love hormone’ could form the basis of treatments of such social functioning disorders as autism.

However, it increasingly appears that oxytocin may have a dark side as well, and that its effect on social interaction is not necessarily always positive.

In the first study, Dutch researchers found that oxytocin increased the in-group/out-group mentality in a person, even to the point of increasing racist feelings towards non-Dutch nationals.

But perhaps even more disturbingly, New York medical school researchers claim to have demonstrated that oxytocin simply increases ones existing capacity to feel trust or suspicion.  Jennifer Bartz set up a social co-operation gaming experiment with both healthy and psychologically ‘unhealthy’ volunteers.  Those with borderline personality disorder left the game earlier if they had been given an dose of oxytocin nasal spray.

Her team studied 14 people diagnosed with borderline personality disorder and 13 volunteers with no psychiatric conditions. Symptoms of borderline personality disorder include severe insecurity about relationships, fears of abandonment and constant, needy reassurance-seeking from partners.

Borderline personality disorder usually occurs in women, but Bartz’s sample included four men. Her group of healthy participants included seven men.

Members of each group played a computer game with an experimenter posing as a research volunteer. In each of three rounds, volunteers had to predict whether their partner would cooperate with them, so that each player could make $6, or if the partner would leave the game in order to claim $4 alone.

Volunteers who suspected the partner of bad intent could leave the game early and claim $4 for themselves.

Borderline personality players of both sexes left the game early far more often after receiving an oxytocin nasal spray than after whiffing a placebo spray. Inhaling the hormone prodded their already high levels of hostile suspicion and depleted minimal reserves of trust, Bartz suggests.

The latest study to appear, however, suggests that oxytocin ought to be termed the ‘hate hormone’ as much as anything else.  Harvard post-doctoral student Jamil Zaki found that oxytocin’s affect on social relationships is not uniquely positive, but appears to enhance the pre-existing attitude towards the relationship.  In particular, the study looked at men’s memories of their early childhood relationship with their mothers.

Thirty-one men ranging in age from 19 to 45 were recruited and given initial psychological tests to measure their childhood attachment to their mothers. The tests determined whether they were anxious about their connection to Mom, avoidant in their dealings with her or secure in the relationship. People who remembered their mothers as having been warm, soothing and responsive tended to be securely attached; those who saw Mom as having been unresponsive, abusive or unreliable were more likely to have attachment anxiety or avoidance

Read more: http://healthland.time.com/2010/11/29/love-hormone-oxytocin-enhances-mens-memories-of-mom-%e2%80%94-good-or-bad/#ixzz16scpYk8I

To no-one’s surprise, both bride and groom had increased levels of oxytocin after the ceremony.  What was also interesting was that relatives and friends in attendance also had their levels measured.  The results of these tests showed that whilst the immediate family of the newly married couple experienced a rise in oxytocin, only two out of five friends did likewise.

Source : Our Happy Hormone Wedding : How the levels of the love hormone oxytocin before and after ceremony

According to researchers at the University of Japan, dog owners experience a surge in the hormone oxytocin after periods of playing with their dogs or simply being gazed at by them. Oxytocin has been nicknamed the “cuddle chemical” for the role it plays in the mother-child bond. It produces positive, warm feelings and because it’s a serious stress reducer – it dampens down the area of the brain associated with anxiety – may also help explain the myriad health benefits associated with dog ownership.

More at : Why owning a dog is good for you

These results provide a possible explanation of why social isolation forms part of the autism spectrum — because an autistic individual’s ability to respond to oxytocin may be limited. Oxytocin has been tied to levels of trust and ability to read social cues.

in­ter­ac­tions with dogs, es­pe­cially those in­i­ti­at­ed by the dog’s gaze, can in­crease the uri­nary [ox­y­to­cin] con­centra­t­ions of their own­ers as a man­i­festa­t­ion of at­tach­ment be­hav­ior.”

Read more about how puppydog eyes trigger oxytocin in owners.