Widely dubbed the love hormone, numerous other names have been given to oxytocin recently - hug hormone, cuddle chemical, moral molecule, bliss hormone - since researchers have begun to uncover its effects on behavior, including its role in love, in addition to its female biological functions in reproduction.

What is oxytocin, and what does it do?

Oxytocin is a hormone that is made in the brain, in the hypothalamus, and it is transported to, and secreted by, the pituitary gland, which is located at the base of the brain.1

Chemically it is known as a nonapeptide (a peptide containing nine amino acids), and biologically, as a neuropeptide. It acts both as a hormone and as a brain neurotransmitter.

The release of oxytocin by the pituitary gland acts to regulate two female reproductive functions:1,2

  • Childbirth
  • Breast-feeding.

The release of the hormone during labor makes the muscles of the uterus, womb, contract - in other words, it increases uterine motility. The release of oxytocin is triggered by the widening of the cervix and vagina during labor, and this effect is in turn increased by the subsequent contractions.3

The main role of oxytocin is summed up nicely in a research paper by obstetric and gynecology specialists Navneet Magon and Sanjay Kalra:2

"It is released in large amounts during labor, and after stimulation of the nipples. It is a facilitator for childbirth and breast-feeding."

Stimulation of the nipples results in oxytocin release and milk let-down.

Other researchers sum up the reproductive importance of oxytocin by saying it "serves the continued propagation of a species," adding that through evolution its "repertoire has expanded to maintain a central role in more complicated aspects of reproductive behavior. For these reasons, we call oxytocin the great facilitator of life."1

Oxytocin, used as a prescription drug, is also known by the brand name Pitocin (and Syntocinon, although this is no longer on the market).4

Doctors prescribe oxytocin to start birth contractions or strengthen them during labor. It is also used to reduce bleeding after child delivery.4,5 The drug also has a role in the medical termination of pregnancy or during miscarriage.5

Oxytocin'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.6

One review of the evidence says oxytocin "has attracted intense attention" after the discovery of its "amazing variety of behavioral functions."6 

The review, by Inga Neumann, says oxytocin has an impact on "pro-social behaviors" and emotional responses that contribute to:6

  • 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."7

Male and female embrace
Oxytocin has been the focus of research into the biology of love.

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.8

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.6

Brain oxytocin also reduces stress responses, including anxiety - and these anxiolytic effects have been demonstrated in a number of species.6,8

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.9

As shown in the recent developments listed here, scientists are still busy testing the behavioral effects of oxytocin and its role in human emotions.

Recent developments about oxytocin's effects on emotion

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 inPsychopharmacology 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.

Oxytocin released during sex

In both men and women, sexual intercourse stimulates the release of oxytocin, which has a role in erection and orgasm. The reason for this is not fully understood, although in women, it has been proposed that the increased uterine motility may help sperm to reach their destination.3

Some researchers believe oxytocin may play a part in the experience of sexual orgasm, proposing a correlation between the concentration of oxytocin and the intensity of orgasm.10

Oxytocin as potential psychiatric therapy

The researcher in the following YouTube video talks about how oxytocin could help people with disorders such as autism to better understand other people's emotions:

The research to uncover oxytocin's "anxiolytic and pro-social influences, beneficial to relief, reproduction, and love" is what has led scientists to describe it as a one of the "most promising neuromodulator/neurotransmitter systems of the brain for psychotherapeutic intervention and treatment of numerous psychiatric illnesses, for example social phobia, autism, and postpartum depression."6

In another research paper, from 2011, the conclusion reads:11

"Oxytocin is of potential use in enhancing interpersonal and individual wellbeing, and might have more applications in neuropsychiatric disorders, especially those characterized by persistent fear, repetitive behavior, reduced trust and avoidance of social interactions."

Recent development on oxytocin as potential therapy

Oxytocin activates "social" brain regions in children with autism. A research study involving 17 children with autism spectrum disorders, published in December 2013, used functional magnetic resonance imaging (fMRI) to see differences created by oxytocin in brain responses to social and non-social pictures. Albeit in a small study, the researchers found "oxytocin temporarily normalized brain regions responsible for the social deficits seen in children with autism."

Written by Markus MacGill

Copyright: Medical News Today

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