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One of the most contentious issues in the vast literature about alcohol consumption has been the consistent finding that those who don't drink tend to die sooner than those who do. The standard Alcoholics Anonymous explanation for this finding is that many of those who show up as abstainers in such research are actually former hard-core drunks who had already incurred health problems associated with drinking.

But a new paper in the journal Alcoholism: Clinical and Experimental Research suggests that — for reasons that aren't entirely clear — abstaining from alcohol does tend to increase one's risk of dying, even when you exclude former problem drinkers. The most shocking part? Abstainers' mortality rates are higher than those of heavy drinkers. (See pictures of booze under a microscope.)

Moderate drinking, which is defined as one to three drinks per day, is associated with the lowest mortality rates in alcohol studies. Moderate alcohol use (especially when the beverage of choice is red wine) is thought to improve heart health, circulation and sociability, which can be important because people who are isolated don't have as many family members and friends who can notice and help treat health problems.

But why would abstaining from alcohol lead to a shorter life? It's true that those who abstain from alcohol tend to be from lower socioeconomic classes, since drinking can be expensive. And people of lower socioeconomic status have more life stressors — job and child-care worries that might not only keep them from the bottle but also cause stress-related illnesses over long periods. (They also don't get the stress-reducing benefits of a drink or two after work.)

But even after controlling for nearly all imaginable variables — socioeconomic status, level of physical activity, number of close friends, quality of social support and so on — the researchers (a six-member team led by psychologist Charles Holahan of the University of Texas at Austin) found that over a 20-year period, mortality rates were highest for those who were not current drinkers, regardless of whether they used to be alcoholics, second highest for heavy drinkers and lowest for moderate drinkers. (Watch TIME's Video "Taste Test: Beer with Extra Buzz.")

The sample of those who were studied included individuals between ages 55 and 65 who had had any kind of outpatient care in the previous three years. The 1,824 participants were followed for 20 years. One drawback of the sample: a disproportionate number, 63%, were men. Just over 69% of the abstainers died during the 20 years, 60% of the heavy drinkers died and only 41% of moderate drinkers died.

These are remarkable statistics. Even though heavy drinking is associated with higher risk for cirrhosis and several types of cancer (particularly cancers in the mouth and esophagus), heavy drinkers are less likely to die than don't drink, even if they never had a problem with alcohol. One important reason is that alcohol lubricates so many social interactions, and social interactions are vital for maintaining mental and physical health. As I pointed out last year, nondrinkers show greater signs of depression than those who allow themselves to join the party.

The authors of the new paper are careful to note that even if drinking is associated with longer life, it can be dangerous: it can impair your memory severely and it can lead to nonlethal falls and other mishaps (like, say, cheating on your spouse in a drunken haze) that can screw up your life. There's also the dependency issue: if you become addicted to alcohol, you may spend a long time trying to get off the bottle. (Comment on this story.)

That said, the new study provides the strongest evidence yet that moderate drinking is not only fun but good for you. So make mine a double.

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