‘Love hormone’ oxytocin also causes aggressive behavior, Israeli scientists find

Widely seen as the ultimate aphrodisiac, oxytocin may also amplify less amiable tendencies, a Weizmann Institute team says

Nathan Jeffay is The Times of Israel's health and science correspondent

Illustrative: A couple arguing (fizkes; iStock by Getty Images)
Illustrative: A couple arguing (fizkes; iStock by Getty Images)

Israeli scientists say they have found that the so-called love hormone, which acts as a social lubricant and spikes during orgasms, may have a less welcome effect: aggression.

Oxytocin, a hormone produced in the brain that hits a high during the first thrilling stages of a relationship, has generated so much excitement in the last decade that one journal study suggested that oxytocin sprays could enhance romantic relationships and help with marriage counseling.

And indeed, manufactured oxytocin sprays are big business online, with sellers claiming they improve sex life and boost both relationships and social interactions (though such assertions should be examined with a healthy dose of skepticism).

Meanwhile, there is also interest among some medical professionals in using the hormone for a variety of conditions, including social anxiety, autism and schizophrenia.

But recently, scientists have started to take a more circumspect attitude, and in a new study published in the scientific journal Neuron, Weizmann Institute of Science researchers say they have concluded that boosting oxytocin may, in fact, do more harm than good.

“We have seen that it is capable of stimulating behaviors we may not want to stimulate, such as aggression,” said Sergey Anpilov, who spent a week supervising 44 mice in a Big Brother-type social experiment in which they competed for food and all their social interactions were filmed and analyzed.

Artist’s image of mice used in the Weizmann Institute of Science research (courtesy of the Weizmann Institute of Science)

Five times a day, Anpilov and his team would use special fiber optic devices mounted on the mice’s heads to alter the function of some of the subjects’ brains.

By turning on specific neurons, they would boost oxytocin levels. Those who weren’t given the oxytocin boost maintained relatively constant behavior while those given the oxytocin boost underwent changes.

At first, the hormone indeed acted as the social lubricant it is widely thought to be. “The resident mice attacked less after having their oxytocin stimulated,” Anpilov told The Times of Israel, adding that they also interacted with each other more.

However, the effect was far from constant.

“On the first day, we saw social interaction was increased and they spent more time with each other, but on the second day they became more aggressive,” said Anpilov.

The mice were in small house-like structures in groups of four, with space to play and interact. Anpilov said that the social element was important as most oxytocin research hasn’t put mice in intense social settings.

Oxytocin-producing cells in a mouse’s brain (courtesy of the Weizmann Institute of Science)

Anpilov is now suggesting that oxytocin isn’t a hormone necessarily associated with love, but rather one that causes people and animals to react more intensely to situations — whether for better or worse.

“Oxytocin doesn’t take you in a specific direction, the direction it takes you in depends on the social situation,” he said, adding that when it has been boosted, social cues appear “amplified.”

Anpilov said that while more research is needed on the topic, the study may have important practical ramifications, specifically in the form of questioning the wisdom of giving oxytocin therapeutically to humans.

“If we assume that oxytocin does the same things in human as [it does in] mice, and we use it for social disorders, we may, in an [unintentional] manner, increase behaviors we don’t want.”

Or in simpler terms: “It may backfire.”

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