Married couples who are heavy drinkers and those who don't drink tend to stay married, but couples with one heavy drinker tend to divorce, U.S. researchers say. Lead author Kenneth Leonard, director of the University of Buffalo Research Institute on Addictions, and co-authors Gregory Homish and Philip Smith of the university's Department of Community Health and Health Behavior, tracked 634 couples from the time of their weddings through the first nine years of marriage. The study, scheduled to be published in the December issue of Psychology of Addictive Behaviors, found couples with only one spouse a heavy drinker had a much higher divorce rate than other couples. For the purpose of the study, heavy drinking was defined as drinking six or more drinks at one time or drinking to intoxication. Over the course of the nine-year study, nearly 50 percent of couples where only one partner drank more heavily ended up divorcing, while the divorce rates for other couples was 30 percent. "This research provides solid evidence to bolster the commonplace notion that heavy drinking by one partner can lead to divorce," Leonard said in a statement. "Although some people might think that's a likely outcome, there was surprisingly little data to back up that claim until now." However, the surprising outcome was that the divorce rate for two heavy drinkers was no worse than for two non-heavy drinkers, Leonard said. "Heavy drinking spouses might 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," Leonard said.