Love & Money is a MarketWatch series looking at how our relationship with money impacts our relationships with significant others, friends and family.

A new study gives a clue to the secret to a long, blissful marriage: genetics.

Yale University researchers concluded that the happiest, most secure-feeling couples in an experiment had at least one person in the pair with a variation in their gene receptor for oxytocin, known as the “love hormone.”

“This study shows that how we feel in our close relationships is influenced by more than just our shared experiences with our partners over time,” said Joan Monin, associate professor at the Yale School of Public Health. “In marriage, people are also influenced by their own and their partner’s genetic predispositions.”

Almost 180 married couples participated in the study, ranging from age 37 to 90. They filled out surveys on marital satisfaction and gave a saliva sample that was used to map their genes.

Oxytocin is linked to bonding and has all kinds of feel-good nicknames like “the cuddle hormone.” It’s also known as a pain reliever.

The study noted researchers have previously looked at the gene variant at issue — termed OXTR rs53576 — for its connection to emotional stability and empathy. The Yale study, however, is thought to be the first looking into its role in a happy marriage.

Businesses like Instant Chemistry and GenePartner let couples see how their genes match up. Instant Chemistry, based in Canada, puts a $149 price on it services, while GenePartner, in Switzerland, charges $249.

Dr. Ron Gonzalez, Instant Chemistry’s co-founder, said the Yale findings were consistent with what his staff has been tracking internally about genetic makeup and oxytocin. Gonzalez said the Toronto-based company has served thousands of people since its 2013 start.

It checks for genes linked to oxytocin, as well as genes associated with how people experience stress and pleasure. The fee includes a psychological profile too.

“It’s a great way to start a conversation to learn about yourself and your partner,” he said.

Shelling out some cash on genetic profiles might be an easy expense, at least compared to the costs of divorce. Amicable divorces where the splitting couples do the paperwork themselves can hover around three digits, but if lawyers get involved and issues get complex and dragged out, those costs can surge far higher.

There’s something to be said for the power of genetic makeup. But there are lots of ingredients in the recipe for long-term romance, like personality mixes, how families mesh and how couples choose to spend their free time.

And, of course, there’s also the role of money in a relationship.

Indeed, a Merrill Lynch study looked into what people wanted most in a partner. Fifty-six percent of the participants said they would prefer a mate who could give them financial security, compared to the 44% who said they were in search of someone who would send them “head over heels.”

Gonzalez himself acknowledges genes are only part of the equation and the extent of their influence is not yet known. “Your predisposition of your genes does not predetermine what you do,” he said — but it might help people be more conscious of their inclinations.

A separate study looked at the same issue of genetic makeup, oxytocin and couples’ chemistry.

That research revealed that less happy husbands, who perceived their spouses as less supportive, had a particular makeup to their gene related to oxytocin.

Even there, the lead researcher cautioned against reading too much into genetic makeup and a solid marital bond. The understanding of chromosomes and couples’ chemistry is just at the very beginning, said Richard Mattson, a psychology professor at Binghamton University, State University of New York.