A new University of Virginia study indicates that people who are married or living together tend to drink less, both fewer drinks and less frequently.
The study also found that singles are more inclined to drink more often, and in larger quantities.
“Intimate relationships cause a decline in alcohol consumption,” said lead study author Diana Dinescu, a Ph.D. candidate in clinical psychology.
For the study, conducted with other researchers at UVA, as well as the University of Southern California and Washington State University, compared the reported drinking patterns of twins in and out of relationships.
Previous research has found that married adults drink less than single or divorced people. For the new study, Dinescu and her colleagues examined the behaviors of 2,425 same-sex twin pairs to see if these findings held up among people who share genetic and familial backgrounds.
Previous studies used more random sample pools that might include unidentifiable variables that could skew results, the researchers noted.
“It is impossible to tell from correlational research whether marital status has a protective effect, or whether people who naturally drink less simply are more likely to get married,” Dinescu said.
“By using twins, our study allows us to eliminate entire classes of alternative explanations, such as genetic predispositions and upbringing influences, and brings us a step closer to understanding the true impact of relationships on drinking behavior.”
The researchers used data from the Washington State Twin Registry, a database of twins who participate in health and behavior research. Their sample included 1,618 female pairs and 807 male pairs.
The twins stated on forms whether they were married, divorced, widowed, separated, never married or living with a partner. They also included information about their level of alcohol consumption, including how much they drank when drinking, and how frequently they drank.
The researchers then compared married twins with their single, divorced, and cohabitating co-twins on drinking frequency and quantity.
What they found is that the married co-twins consumed less alcohol than their single or divorced co-twins and also drank less frequently. Cohabitating twins, like their married cohorts, consumed less alcohol than single or divorced twins.
Interestingly, the researchers also discovered that cohabitating participants generally drank more frequently than married men and women, but less than their single, widowed, and divorced counterparts. Cohabitating men, however, drink fewer alcoholic beverages per occasion than married men, while cohabitating women drink about the same in one sitting as their married counterparts.
The study concluded that once a relationship is over, people may be more inclined to drink more heavily in a session, but not necessarily more frequently.
“It is useful to look at drinking frequency and quantity separately, as we believe they are fundamentally different behaviors in both intention and venue,” Dinescu said. “Our data revealed an interesting pattern where, once you’re in a committed relationship, your drinking frequency declines permanently, whereas quantity goes back up if you exit that relationship.”
“It seems that intimate relationships may provide a real benefit in terms of drinking behavior, maybe through mechanisms such as a monitoring effect that partners have on each other,” she concluded.
The study was published in the Journal of Family Psychology.