It is sometimes known as the "cuddle hormone" or the "love hormone," because it is released when people snuggle up or bond socially, according to Texas Medical Center. Even playing with your dog can cause an oxytocin surge, according to research published in 2017 in the journal Frontiers in Psychology. But these monikers may be misleading.
According to the American Psychological Association, oxytocin can also intensify memories of bonding gone bad, such as in cases where men have poor relationships with their mothers. It can also make people less accepting of people they see as outsiders. In other words, whether oxytocin makes you feel cuddly or suspicious of others depends on the environment.
Oxytocin in women
Oxytocin is a particularly important hormone for women. "Oxytocin is a peptide produced in the brain that was first recognized for its role in the birth process, and also in nursing," said Larry Young, a behavioral neuroscientist at Emory University in Atlanta, Georgia.
The hormone increases the strength and frequency of uterine contractions during labor and helps shrink the uterus after delivery, according to a chapter in the book "Drugs During Pregnancy and Lactation" (Elsevier B.V., 2015). When an infant suckles at their mother's breast, the stimulation causes the mom's body to release oxytocin, which, in turn, orders the body to "let down" milk for the baby to drink.
Oxytocin also promotes mother-child bonding. Studies show that "female rats find pups to be aversive if [the females are] virgins," Young told Live Science. "But once they give birth, the brain is transformed, so they find the pups irresistible," he said. And similar findings are seen in humans.
The Association of Psychological Science found that the higher a mom's oxytocin levels in the first trimester of pregnancy, the more likely she was to engage in bonding behaviors such as singing to or bathing her baby.
Related: 11 interesting effects of Oxytocin
Although maternal bonding may not always be hardwired — after all, human females can adopt babies and take care of them — oxytocin released during pregnancy "does seem to have a role in motivation and feelings of connectedness to a baby," Young said. Studies also show that interacting with a baby causes the infant's own oxytocin levels to increase, he added.
Oxytocin in men
In men, oxytocin also facilitates bonding. In previous research, dads who got a boost of oxytocin via a nasal spray played more closely with their 5-month-old babies than dads who didn't get the hormone zap, Live Science reported. (There is another hormone, called vasopressin, which plays a stronger role in bonding for men.)
This anti-social effect of a social hormone brings some nuance to the story of oxytocin. In one study, researchers found that Dutch students given a snort of the hormone became more positive about fictional Dutch characters, but they were more negative about characters with Arab or German names.
The finding suggests that oxytocin's social bonding effects are targeted at whomever a person perceives as part of their in-group, the researchers reported in January 2011 in the Proceedings of the National Academy of Sciences (PNAS).
In another study, also published in PNAS, men were given a dose of oxytocin and asked to recall memories of their mothers. Those with secure relationships described their moms as more caring after the hormone dose.
Those with troubled relationships actually saw their mothers as less caring than they did before receiving the dose. The hormone may help with the formation of social memories, according to the study researchers, so a whiff strengthens previous associations, whether good or bad.
"My view of what oxytocin is doing in the brain is making social information more salient," Young said. "It connects brain areas involved in processing social information — whether it's sights, faces, sounds or smells — and helps link those areas to the brain's reward system."
Oxytocin and anxiety
As well as creating social bonds and developing trust between people, oxytocin can also create opposing responses. According to a study in mice that was published in 2020 in PNAS, anxiety and envy can result when oxytocin is made in a certain part of the brain, the researchers said in a statement.
Usually, oxytocin is produced in an area of the brain called the hypothalamus. Sometimes, however, the hormone is produced in the "bed nucleus of the stria terminalis" (BNST). This part of the brain plays a key role in the body's stress response.
In the study, the researchers analyzed the brains and behaviors of mice, found that the mice displayed signs of social anxiety when oxytocin was produced in the BNST.
What are oxytocin sprays?
Oxytocin nose sprays also have been considered for use in treating autism, a neurological disorder marked by struggles with social functioning, Live Science previously reported. Research published in 2017 in the journal PNAS shows that increased levels of oxytocin in children with autism could improve their social abilities.
In this study, which involved 32 children ages 6-12, scientists found that this treatment had the biggest impact on those who had the lowest natural levels of oxytocin beforehand.
"When you think about using oxytocin to treat autism, you want to make sure you do it in a context where the social information is positive," Young said.
Use of oxytocin sprays outside of a medical context is far murkier, however. The sprays sold online without a prescription promise stress relief and social ease. In 2019, they were approved by the Food and Drug Administration (FDA), specifically for treatment-resistant depression. For other treatments, little is known about the sprays' efficacy and side effects.
There are no long-term studies on the side effects of the legitimate oxytocin sprays used in hormone research; most studies give people one dose of the hormone only. Pitocin, a synthetic version of oxytocin given intravenously to stimulate labor, according to Healthline. This can prevent complications in overdue births, but also holds risks such as infection and overstimulation of the uterus.
- Video: What hormones are involved in love and separation?
- American Psychological Association: The Two Faces of Oxytocin
- University of California Berkeley: 'Trust Hormone' Oxytocin Helps Old Muscle Work Like New, Study Finds
This article is for informational purposes only, and is not meant to offer medical advice.
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Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.