Why do some people have an easier time with relationships than others? The answer could be genetic.

Researchers found a gene that regulates serotonin can also predict how one's emotions will play out in a relationship, a University of California, Berkeley press release reported.

"An enduring mystery is, what makes one spouse so attuned to the emotional climate in a marriage, and another so oblivious?" UC Berkeley psychologist Robert W. Levenson, senior author of the study, said. "With these new genetic findings, we now understand much more about what determines just how important emotions are for different people."

The researchers "found a link between relationship fulfillment and a gene variant," (allele) called 5-HTTLPR.

People who inherited two short 5-HTTLPR alleles were found to be most unhappy when there were negative emotions within the marriage, but also most happy when the marriage was going well. Individuals with longer alleles were less likely to be bothered by emotional turmoil.

"We are always trying to understand the recipe for a good relationship, and emotion keeps coming up as an important ingredient," Levenson said, who heads up a longitudinal study that has tracked over 150 married couples for more than 20 years.

The researchers said people with different variations of 5-HTTLPR can still work as a couple, the finding simply suggests people with two short alleles are more likely to do well in a good relationship, and also are more likely suffer in a bad one.

"Individuals with two short alleles of the gene variant may be like hothouse flowers, blossoming in a marriage when the emotional climate is good and withering when it is bad," Claudia M. Haase, assistant professor of human development and social policy at Northwestern University and lead author of the study, said. "Conversely, people with one or two long alleles are less sensitive to the emotional climate.

"Neither of these genetic variants is inherently good or bad. Each has its advantages and disadvantages," she said.

In the study, researchers analyzed 156 middle-aged and senior couples whose relationships had been followed by researchers since 1989. Every five years the participants reported on their satisfaction in their marriage.

Recently, 125 of the couples provided DNA samples which helped the researchers make the connection.