The findings could help researchers find strategies to overcome the negative effects of alcohol on human relationships. Image: Shutterstock.

Males who drink alone spend less time with their original female partner compared to couples where both drink alcohol and those which never drink.

 — By Conn Hastings

A study of the effect of alcohol on long-term relationships finds that when a male prairie vole has access to alcohol, but his female partner doesn’t, the relationship suffers – similar to what has been observed in human couples. The study, published today in open-access journal Frontiers in Psychiatry, also identifies changes in a specific brain region in the male voles. The findings could help researchers find strategies to overcome the negative effects of alcohol on human relationships.

Alcohol is sometimes described as a “social lubricant” that can help people to socialize. However, problematic drinking can have devastating effects on human relationships. “We know that heavy drinking is associated with increased separation rates in couples in which one of the partners is a heavy drinker and the other is not, while separation rates don’t seem to increase when both partners drink in a similar manner, or don’t drink at all,” says Andrey Ryabinin, of Oregon Health & Science University.

Human relationships are complex, and can be affected by a variety of factors, such as financial difficulties or infidelity. Researchers don’t know if problematic drinking directly contributes to relationships breaking down, or if the unhappiness people experience in failing relationships drives them to drink. Understanding whether alcohol’s effects on the brain directly contribute to relationship breakdown could help researchers to understand and treat problematic human behaviour.

So, how can scientists study this complex phenomenon? One option is the humble prairie vole, a small rodent found in North America. “Not many rodents form long-term social attachments and not many rodents like to drink alcohol,” says Ryabnin. “However, prairie voles are unusual as they are socially monogamous and like drinking alcohol, so they are perfect to investigate the role of alcohol in relationships.”

Andre Walcott, a graduate student in Ryabinin’s laboratory, allowed male and female prairie voles to form social bonds over one week. The researchers then gave the males access to a 10% alcohol solution, while their female partners were allowed only water (discordant drinking) or also had access to alcohol (concordant drinking). In a control group, both males and females had access to water only.

To test how strong the social bond in each couple was, the researchers gave each male a choice between huddling up beside his female partner or a new female. By timing how long the male spent beside each female, the researchers could measure how strong the bond between the male and the original female was.

The team found that the prairie vole couples behaved like human couples in terms of how alcohol affected their relationships. During the social connection test, males who had drunk alone spent less time with their female partner, whereas those who had never drunk or those who had drunk alongside their partner huddled with them for longer.

These results mean that discordant drinking can directly affect prairie voles’ relationships, and the researchers set out to investigate if there were any changes in the brains of the male prairie voles. Sure enough, in the males who had drunk alone, they identified changes in a brain region called the periaqueductal grey that might be responsible for these effects.

So, what does this mean for human couples? “Our results in prairie voles have identified a biological mechanism that could explain the link between discordant drinking and relationship breakdown, but we will need to do further work to confirm this for humans.” says Ryabinin. “In future studies, we might be able to find strategies to overcome the negative effects of alcohol, to improve relationships that are disrupted by problematic drinking”.

Original research article: Alcohol’s Effects on Pair-Bond Maintenance in Male Prairie Voles

Corresponding author: Andrey E. Ryabinin

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