MONDAY, Sept. 1 (HealthDay News) -- Whether a man has one type of gene versus another could help decide whether he's good "husband material," a new study suggests.

A study of Swedish twin brothers found that differences in a gene modulating the hormone vasopressin were strongly tied to how well each man fared in marriage.

"Our main finding was an association between a variant of the vasopressin receptor 1a gene and how strong bonds men reported they had to their partners," said lead researcher Hasse Walum, of the department of medical epidemiology and biostatistics at the Karolinska Institute in Stockholm. "Men carrying this variant scored on average lower on a scale measuring the strength of the bond compared to men not carrying this variant."

Women married to men carrying the "poorer bonding" form of the gene also reported "lower scores on levels of marital quality than women married to men not carrying this variant," Walum noted.

His team published its findings in this week's issue of the Proceedings of the National Academies of Science.

Walum's team first got interested in the role of vasopressin and bonding among males when studying a rodent, the vole. "Studies in voles have shown that the hormone vasopressin is released in the brain of males during mating," Walum explained.

Vasopressin activates the brain's reward system, and "you could say that mating-induced vasopressin release motivates male voles to interact with females they have mated with," Walum said. "This is not a sexual motivation, but rather a sort of prolonged social motivation." In other words, the more vasopressin in the brain, the more male voles want to stick around and mingle with the female after copulation is through. This effect "is more pronounced in the monogamous voles," Walum noted.

But voles and humans are very different species, so would the same effect hold true for men?

To find out, the Swedish team zeroed in the vasopressin 1a gene, which is shared by both species. Variations in this gene strongly influence vasopressin activity in the male vole, so Walum wondered if it might do the same for men.