The “love hormone” that bonds a mother and child, and which also plays an important role in forming sexual attachments, is more involved in our friendships and social lives than we previously understood.
In a new study published in Nature, researchers found that because oxytocin is so crucial to our social interactions, it may offer clues to unlock treatments for social aversion, which could help people with depression, mental disorders, and autism.
Dr. Robert Malenka, a professor of psychiatry and behavioral sciences at Stanford, and Dr. Gül Dölen, assistant professor at the Johns Hopkins Brain Science Institute, discovered that the way oxytocin changes the activity in the reward center of our brain influences our feelings of pleasure during social interaction.
This offers greater insight into the significant impairments associated with social aversion.
“It is critical to understand the underlying abnormalities in brain function that cause the deficits in social behavior,” Malenka told Seeker. “These deficits profoundly affect these individuals’ quality of life.”
“There is plenty of evidence that social interactions are vital for human health,” Dölen added. “Diminished social network size is correlated with… an effect that is equal to or greater than the negative effects of smoking, alcohol, obesity, and pollution.”
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An oxytocin nasal spray has already been administered to autistic children in clinical trials with mixed results, but the new study validates further exploration of oxytocin as a treatment for brain disorders that impair social activity.
Malenka and Dölen wanted to examine the neurological process behind the enjoyment we feel when hanging out with friends. They chose to focus their research on the activity of a part of the brain’s reward system, the nucleus accumbens, using trials with mice.
The team created a small two-room house for the animals, then put them all together in one room for 24 hours. Each mouse then spent the next 24 hours alone in the other room. When they put the rooms together and allowed the mice to roam freely, the hypothesis was that they would opt for the room where they had fun hanging out with their friends.
This turned out to be true, but when the mice had their oxytocin receptors blocked, they no longer felt like socializing and instead chose to be alone in the other room. This was the only notable difference in the mice.
“When we inhibited these oxytocin neurons when the subject mouse was alone, there were no observable effects on its behavior,” Malenka said.
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Using advanced technical experiments that took nearly four years of work, the research team located the oxytocin receptors of the mice inside the nucleus accumbens. These receptors lie at the tips of nerve cells that form a path from another brain region called the dorsal Raphe.
This is significant because the dorsal Raphe also releases serotonin. Some popular anti depressants like Zoloft and Prozac work by increasing the serotonin levels in this part of the brain, which triggers activity in the nucleus accumbens, resulting in happy feelings.
“The study suggests that one factor contributing to social behavior deficits may be abnormal modulation of the brain’s reward circuitry by oxytocin,” Malenka said.
But oxytocin isn't the whole story.
“Social behaviors are very complex,” he noted, “and will involve lots of different brain regions and brain ‘circuits.’”
Malenka hopes his team’s findings will someday help to develop drugs to treat autism and other disorders that impair social interactions, but there’s another reason why he believes studying the brain’s reward system is important.
“At a time when there is enormous tension between individuals and societies with different world views,” he commented, “what is more important than understanding what allows us to feel good about each other?”
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