Oxytocin keeps attached men away from hot women

By MyHealthNewsDaily Staff
MyHealthNewsDaily

The “love hormone” oxytocin may help maintain romantic relationships by prompting men to keep their distance from attractive women, a new study from Germany suggests.

In the study, men in monogamous relationships who were given an oxytocin nasal spray stayed about four to six inches farther away from an attractive, woman they didn’t know, compared with men in monogamous relationships who received a placebo.

The oxytocin spray had no effect on the distance that single men chose to keep between themselves and the attractive woman.

The results suggest the hormone promotes fidelity in humans, said study researcher Dr. René Hurle­mann, of the University of Bonn. The findings agree with previous research conducted on prairie voles, which suggested the hormone plays a role in pair-bonding.

In humans, oxytocin has been found to promote bonding between parents and children, increase trust, and reduce conflict between couples. And earlier this year, a study found that couples with high levels of oxytocin in the early stages of a relationship were more likely to be together six months later than couples with lower levels of the hormone.

But until now, there has been no evidence that a dose of oxytocin given after a couple gets together contributes to the maintenance of the relationship, the researchers said.

The study involved 57 heterosexual males, about half of whom were in monogamous relationships. After receiving either a dose of oxytocin or placebo, participants were introduced to a female experimenter who they later described as “attractive.”

During the encounter, the experimenter moved towards or away from the men, and they were asked to indicate when she was at an “ideal distance” away, as well as when she moved to a distance that felt “slightly uncomfortable.”

The effect of oxytocin on the attached men was the same regardless of whether the female experimenter maintained eye contact, or averted her gaze. Oxytocin also had no effect on the men’s attitude toward the female experimenter — whether men received the oxytocin or the placebo, they rated her as being equally attractive.

In a separate experiment, the researchers found oxytocin had no effect on the distance men kept between themselves and a male experimenter.

Future studies are needed to determine exactly how oxytocin might act on the brain to affect behavior, the researchers said.

The study will be published Nov. 14) 2012  in The Journal of Neuroscience.

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Oxytocin —the so-called “love hormone” — is being increasingly shown to trigger a wide variety of physical and psychological effects in both women and men.

The hormone’s influence on our behavior and physiology originates in the brain, where it’s produced by the by a structure called the hypothalamus, and then transfers to the pituitary gland which releases into the bloodstream.. Like antennas picking up a signal, oxytocin receptors are found on cells throughout the body. Levels of the hormone tend to be higher during both stressful and socially bonding experiences, according to the American Psychological Association.

“It’s like a hormone of attachment, you might say,” said Carol Rinkleib Ellison, a clinical psychologist in private practice in Loomis, California and former assistant clinical psychiatry professor at the University of California, San Francisco. “It creates feelings of calm and closeness.”

Thought scientists have long  known about oxytocin’s rolein breastfeeding and childbirth, “We’re just learning more about it now,” Ellison said.

A stream of studies in the last decade have focused on oxytocin’s effects on body and mind. Here’s a look at what we’ve learned.

 

Pregnant women with higher levels of oxytocin during their first trimester bonded more strongly with their babies after they were born, according to a 2007 study in the journal Psychological Science. And compared with other women, women with higher levels throughout their pregnancy and in the first month after birth reported engaging in more behaviors — such as singing, feeding and bathing their infants in specific ways — that promoted an exclusive relationship between the two, the study found.

 

Comparing urine levels of oxytocin and a related hormone called vasopressin in biological and adoptive children who lived in Russian and Romanian orphanages, researchers found that oxytocin rose in biological children after having contact with their mothers. The study, published in 2005 in the journal Proceedings of the National Academy of Sciences, showed that oxytocin levels remained static in the adoptive children in the same situation, suggesting a physiological basis for why some adoptive children have difficulty forming secure relationships.

 

Research done on prairie voles showed that those separated from their siblings exhibited signs of anxiety, stress and depression that abated after they were injected with oxytocin. The study, presented at a 2007 meeting of the Society for Neuroscience, indicated the hormone’s effects were more evident under stressful situations.

 

A November study in the journal Proceedings of the National Academy of Sciences supported researchers’ theory that oxytocin would amplify men’s early memories of their mothers. In a group of 31 men, those who inhaled a synthetic version of the hormone found the hormone intensified fond memories of their mothers if their relationships had been positive. Those whose ties with their mom’s had frayed downgraded their opinions after inhaling oxytocin, the study showed.

 

In its best understood role, oxytocin is released in large amounts during labor, intensifying the uterine contractions that open the cervix and allow the baby to pass through the birth canal. Physicians have been using synthetic oxytocin, also known by its brand name Pitocin, to induce or augment labor since the early 1900s. After birth, the hormone continues to stimulate uterine contractions that discourage hemorrhaging, and more is released when the nipples are stimulated during suckling, promoting the letdown of milk into the nipples.

 

Spontaneous erections in rats were observed after oxytocin was injected into their cerebrospinal fluid in a 2001 study in the journal Physiological Review. And a cocktail of brain chemicals that includes oxytocin is released in men during ejaculation. These chemicals can intensify bonding between sexual partners , though, Ellison noted, “it isn’t the same for everyone.”

“I think there is a variability,” said Ellison, who also teaches sexuality classes to health professionals. “For people who can really get into the sensualness of hugging and cuddling, that is the hormone released in this process. For people who don’t get into it, maybe they’re not releasing the oxytocin. It may be a circular thing.”

 

According to a 1999 article in the journal Progress in Brain Research, some studies indicate that oxytocin inhibits tolerance to addictive drugs, including opiates, cocaine and alcohol , and reduces withdrawal symptoms. “It’s an antidote to craving,” Ellison explained. “That craving (for drugs), that hunger, is probably eased with this hormone. It’s involved with the satisfaction of hunger.”

 

A February study in the journal Proceedings of the National Academy of Sciences showed that inhaling oxytocin significantly improved the ability of people with autism to interact with others. Previous studies indicated natural oxytocin levels were lower in those with autism, a developmental disorder characterized by difficulties in communication and social relationships. Oxytocin also reduced autistic individuals’ fear of others, researchers said.

 

A June study in the journal Science suggested oxytocin triggers defensive aggression against outsiders who might threaten someone’s social group, such as in soldiers who defend their comrades. Prior animal studies had shown that the hormone promotes protectionist behavior, but this research was the first to demonstrate a similar effect in humans.