The secret to a happy marriage seems to be a never-ending topic of discussion, but Robert Levenson, a psychology professor at UC Berkeley, is taking a closer look — all the way to the cellular level, in fact.

A new video from Fig. 1 — a web series from the University of California that focuses on new ideas and research surrounding science, art and more — visits the topic of whether DNA can effect nuptial bliss. And according to Levenson, that answer is yes.

One ongoing study, Levenson explains, started in 1989 and follows 156 middle-aged and older couples, 125 of whom gave DNA samples. Every five years, they’re quizzed by researchers about their marital satisfaction.

“Some couples are in these relationships that are very emotionally difficult — a lot of anger and sadness and contempt. And the marriages just get really miserable,” Levenson says in the video. “Others have similarly toxic environments, but they seem to do okay. So this was not what we were expecting … and we started thinking that, maybe, the answer lies in their genes.”

Twenty-six years in, Levenson believes one factor is the gene that distributes serotonin, or the “happy” chemical in our brains. One common variation in the gene leads to bigger emotional responses in those who carry it; while the difference may be slight, he points out, over time all those responses can have a cumulative effect in a long-term relationship.

Happy wife, happy life? It may be time to update that saying.

Watch the video above to learn how Levenson believes something as small as a cell can make all the difference.

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