People who are prone to alcohol dependence are more likely to choose a partner who is also at risk, according to a new study.
Scientists at the Washington University School of Medicine in St Louis have found that the situation is more complex than this, however, because - in many cases - the problems endured by one partner can protect the other from falling into the same traps.
The study, published in the May issue of Alcoholism: Clinical & Experimental Research, begins with the assertion that alcohol dependence is influenced by both genetics and environmental factors.
"There's lots of room for different factors to influence the behaviour of two people who are married," said report author Dr Julia D Grant. "One spouse could work at a place where the co-workers go out for a drink after work. Or one spouse could be a regular churchgoer, while the other prefers to sleep.
"As they say, 'like marries like,'" she added. "Spouse selection is not a random process, and we call this non-random mating. People tend to choose mates who are similar to them, not only from the same neighbourhood or socio-economic background but also alike in personality and other behaviours. We found that people at risk for alcohol dependence tend to marry others who are at risk."
Most significant, however, is the finding that the additional influence of a partner's excessive alcohol consumption tends to reduce the risk of a second case of alcoholism developing. When one partner starts to abuse alcohol, the other is often seen to reduce alcohol intake significantly.
"We don't really know how this works," Dr Grant added. "It is possible that an individual decreases his or her alcohol consumption in reaction to the other's excessive alcohol use. Maybe one person is responsible for getting the kids up and out for school in the morning, for example."
Earlier this week, researchers in America argued that alcohol consumption actually shrinks the brain. People consuming more than 14 drinks per week were found to have suffered a 1.6 per cent reduction in brain volume in comparison to those who never drank.
Significantly, the effects were most marked in females, who appear to be more sensitive to the detrimental impact of alcohol consumption.
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