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Oxytocin: 'Love Hormone' Demystified


 

 Oxytocin: 'Love Hormone' DemystifiedOxytocin's effects on emotion

Oxytocin is released into the bloodstream to produce its classic effects on the uterus and breast milk, but it is also released into defined regions of the brain that are involved in emotional, cognitive, and social behaviors.

One review of the evidence says oxytocin "has attracted intense attention" after the discovery of its "amazing variety of behavioral functions." The review, by Inga Neumann, says oxytocin has an impact on "pro-social behaviors" and emotional responses that contribute to:

  • Relaxation

  • Trust

  • Psychological stability.

However, another review notes that the hormone does not act alone in the chemistry of love, but is "just one important component of a complex neurochemical system that allows the body to adapt to highly emotive situations."
 

Another review has also sounded caution, calling for research to look more to the general effects than to the specific effects of oxytocin that are being interpreted. "After all, it is rather unlikely that any widely acting hormone or neurotransmitter will be narrowly funneled to modulate complex, high-order mental processes that are specific to social cognition," say the authors of a 2013 paper.

Scientific research has nonetheless uncovered brain oxytocin's specific ability to modulate social behavior, including effects on motherly care and aggression, bonding between couples, sexual behavior, social memory, and trust. Brain oxytocin also reduces stress responses, including anxiety - and these anxiolytic effects have been demonstrated in a number of species.

One of the so-called 'love hormone' studies was published in 2012, and it examined oxytocin levels in new lovers versus those in single people. It found that there were high levels of the hormone in the first stages of romantic attachment, and these were sustained for six months. 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 sensuousness 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.

 Oxytocin: 'Love Hormone' DemystifiedOxytocin released in the brain under stress-free conditions naturally promotes sleep , according to a 2003 study in the journal Regulatory Peptides. Ellison said this link makes sense because oxytocin counters the effects of cortisol, which is the known as the stress hormone. "It has a calming effect," she said. "It leaves you feeling tranquil and loving, and certainly that helps our path to sleep."

In a 2007 study in the journal Public Library of Science ONE, participants inhaled oxytocin or a placebo through their noses, and then were given a decision on how to split money with a stranger. Those on oxytocin were 80 percent more generous, researchers said, and the hormone seemed to affect their sense of altruism as well.

Oxytocin: the monogamy hormone. This study, published in the journal PNAS in November 2013, examined brain scans of men who had received oxytocin or placebo via a nasal spray. The oxytocin was associated with activation of the men's reward centres in their brains, and with greater feelings of attraction to their partners versus other women in photographs. This followed a very similar study in The Journal of Neuroscience in November 2012: A hormone can help keep men faithful.

High oxytocin levels "trigger oversensitivity to emotions of others." Released in January 2014, this study in Emotion found that people receiving oxytocin nasal spray saw facial expression of emotions in others more intensely.
 

Oxytocin makes you feel more extroverted. This 2011 research paper in Psychopharmacology gave results from intranasal oxytocin improving self-perception in social situations, amplifying personality traits such as warmth, trust, altruism and openness. The hormone that allows us to love may also encourage us to lie. This 2014 study found participants given oxytocin were more likely to lie for the benefit of the group.

With so many studies done and still going on, oxytocin the "love hormone" still remains to be fully understood and explored. But the above discussions goes a long way in demystifying its secrets and its effect in human beings.

 

 

 

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Dated 12 May 2015

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