Men’s marital behavior may be influenced by vasopressin receptor gene

A variant of a gene for a peptide hormone receptor has been implicated in marital discord

The peptide hormone arginine vasopressin (AVP) has long been associated with pair-bonding behavior in highly social animals such as the prairie vole.  Present in many mammals, its primary function is to control water retention.  When you’re dehydrated it is released into the blood stream from the posterior pituitary, and induces the kidneys to conserve water.  It also raises the blood pressure through vasoconstriction (narrowing of the blood vessels).  Researchers have also found a variety of neural effects, the most interesting of which is its role in pair bonding.

One theory is that it is released during sexual behavior, and stimulates and sustains such behavior.  It is also believed to make the male more aggressive towards other males.  The distribution of vasopressin receptors seems to be different in pair-bonding species such as prairie voles and promiscuous species such as meadow voles, which supports the idea of a link.

As of now the role of vasopressin, if any, in human pair bonding is unknown and has not been established.  A forthcoming paper in the Proceedings of the National Academy of Sciences by a team of Swedish genetic epidemiologists from the Karolinska Institutet in Stockholm may change that.

Hasse Walum, a postgraduate student at the Institute, examined the distribution of a gene that codes for the vasopressin receptor type 1a (AVPR1a) in the human brain, using data from the Swedish Twin Offspring Study led by Paul Lichtenstein.   About 500 volunteer couples who had been together at least five years filled in questionnaires designed to measure the quality of their experience of monogamy.  Walum reports that the study found a correlation between one variant, named allele 334, and marital conflict.  Just 15% of men with no copies of allele 334, or one, had had a marital crisis in the past year, but more than twice that many men with two copies of allele 334, 34%, reported such a crisis.  Two of every five men have either one or two copies of allele 334.

In 2005, Larry Young of Emory University School of Medicine, Atlanta, reported in Science that a variant of the gene correlated with the quality of pair-bonding in male pairie voles.  He cautiously welcomes the Swedish finding, but says he is “skeptical until this can be replicated.”

UPDATE: Adding new links.

UPDATE: This has now been published by PNAS on the web

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