Love Is a Chemical Reaction, Scientists Find

Young, a researcher at the Yerkes National Primate Research Center at Emory University in Atlanta, studies the neurobiology that underlies pair bonds — what nonscientists might call love.

In an essay in the journal Nature last month, he laid out evidence that scientists may soon be able to tie the emotion “love” to a biochemical chain of events, and might someday even be able to develop drugs that enhance social bonding — in much the same way that pharmaceuticals today can help regulate emotions like anxiety and depression.

But, Young says, it’s not a love potion. “The holy grail is a drug that might be able to enhance the social abilities of people with social disorders like autism.”

In his lab at Yerkes, Young studies rodents called prairie voles. Unlike 95 percent of mammals, prairie voles mate for life.

“They form a lifelong bond,” Young said. “They nest together, they raise a family together, they have another litter. So they have this really intense bond between them.”

In a series of studies, Young found that the hormones that produce that bond are the same ones that promote parent-child bonding in many other species.

For females, that hormone is oxytocin.

“We can take a prairie vole female, inject her with oxytocin, and she’ll bond with whatever male is around,” Young said.

For males, a related hormone called vasopressin promotes both pair bonding and fatherly behaviors like grooming young voles.

But like humans, some voles are more suited for monogamy than others. In one recent study, Young found that male voles with a particular variant of a gene called AVPR1A that codes for vasopressin receptors in the brain had fewer of those receptors than usual. And so, perhaps not surprisingly, voles with that gene variant were less likely to bond with females than voles without it.

In another study, Young found that implanting a version of the AVPR1A gene in meadow voles — a related species that does not mate for life — produced never-before-seen monogamous meadow voles.

Recently, Swedish researcher Hasse Walum of the Karolinska Institute in Stockholm found that a related gene in human males has similar effects.

In a study published in September in the Proceedings of the National Academies of Science, Walum studied a version of the AVPR1A gene that codes for vasopressin receptors in men. He studied more than 1,000 Swedish men, and found that men who carried a particular variant of the gene were less likely to be married than men without the variant, were more likely to report a recent crisis in their marriage, and ranked lower on a scale of partner bonding that asked questions such as “how often do you kiss your mate?”

Now, Walum and his colleagues are studying whether there are similar relationships between oxytocin receptors and pair bonding in women — a more difficult study, he says, because there are no genes with as straightforward a relationship to oxytocin receptors as the AVPR1A gene has to vasopressin receptors in males.

Walum’s study generated volumes of both scientific and popular interest, with headlines suggesting that cheating males could just blame their genes. But he cautions against overinterpreting his results.

“There are many things that influence marital happiness, and this gene variant is only a small part of that variation,” he said. “A genetic test would not be very important in choosing a mate … getting to know each other would be better.”

Meanwhile, some marketers are already trying to take advantage of the work of Young, Walum and other scientists. An Internet company called Vero Labs sells a product called “Enhanced Liquid Trust,” a mix of oxytocin and pheromones the company claims will enhance your dating life.

Although Young does believe that scientists may someday develop bonding-enhancement drugs, he said that that day is still far in the future.

The companies selling online love potions now, he said “are basing it on some science, but their strategy is completely crazy. … It’s all just baloney.”