BUFFALO, N.Y. - Do drinking and marriage mix? That depends on who's doing the drinking -- and how much -- according to a recent study by the University at Buffalo Research Institute on Addictions (RIA).

Researchers followed 634 couples from the time of their weddings through the first nine years of marriage and found that couples where only one spouse was a heavy drinker had a much higher divorce rate than other couples.

But if both spouses were heavy drinkers? The divorce rate was the same as for couples where neither were heavy drinkers.

"Our results indicate that it is the difference between the couple's drinking habits, rather than the drinking itself, that leads to marital dissatisfaction, separation and divorce," said Kenneth Leonard, PhD, RIA director and lead author of the study.

A video interview with Leonard about the research is available here: http://youtu. be/ AhRDOJG75CU .

The study's co-authors were Gregory Homish, PhD, and Philip Smith, PhD, of UB's Department of Community Health and Health Behavior.

Over the course of the nine-year study, nearly 50 percent of couples where only one partner drank more heavily wound up divorcing, while the divorce rates for other couples was only 30 percent. ("Heavy drinking" was defined as drinking six or more drinks at one time or drinking to intoxication.)

"This research provides solid evidence to bolster the commonplace notion that heavy drinking by one partner can lead to divorce," Leonard said. "Although some people might think that's a likely outcome, there was surprisingly little data to back up that claim until now."

The surprising outcome was that the divorce rate for two heavy drinkers was no worse than for two non-heavy drinkers. "Heavy drinking spouses may be more tolerant of negative experiences related to alcohol due to their own drinking habits," Leonard said. But he cautioned that this does not mean other aspects of family life are unimpaired. "While two heavy drinkers may not divorce, they may create a particularly bad climate for their children."

The researchers also found a slightly higher divorce rate in cases when the heavy drinker was the wife, rather than the husband. Leonard cautions that this difference is based on only a few couples in which the wife was a heavy drinker, but the husband was not, and that the finding was not statistically significant. He suggests that if this difference is supported by further research, it might be because men view heavy drinking by their wives as going against proper gender roles for women, leading to more conflict.

The study controlled for factors such as marijuana and tobacco use, depression and socioeconomic status, which can also be related to marital dissatisfaction, separation and divorce.

"Ultimately, we hope our findings will be helpful to marriage therapists and mental health practitioners who can explore whether a difference in drinking habits is causing conflicts between couples seeking help," Leonard said.

The study was supported by the National Institute on Alcohol Abuse and Alcoholism and the findings will appear in the December issue of Psychology of Addictive Behaviors.

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RIA is a research center of the University at Buffalo and a national leader in the study of alcohol and substance abuse issues. RIA's research programs, most of which have multiple year funding, are supported by federal, state and private foundation grants. Located on UB's Downtown Campus, RIA is a member of the dynamic Buffalo Niagara Medical Campus and helps promote UB's strategic focus on research initiatives.