Oxytocin is a hormone secreted by the posterior lobe of the pituitary
gland, a pea-sized structure at the base of the brain.
It's sometimes known as the "cuddle
hormone" or the "love hormone," because it is released when
people snuggle up or bond socially. Even playing with your dog can cause an
oxytocin surge, according to a 2009 study published in the journal Hormones and
Behavior. But these monikers may be misleading.
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 causes uterine contractions during
labor and helps shrink the uterus after delivery. When an infant suckles at his
or her mother's breast, the stimulation causes a release of 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.
A 2007 study published in the journal
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. [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, as in women, oxytocin facilitates bonding.
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, a 2012 study
found. (There is another hormone, called vasopressin, which plays a stronger
role in 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 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 journal PNAS.
In another study, published in PNAS in 2010, men
were given a dose of oxytocin and asked to write about 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. 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."
