(27.09.2009) When it comes to alcohol consumption and depression, a new study by a team of Norwegian and British researchers shows that heavy drinkers – but also teetotalers -- have higher levels of depression and anxiety than those who drink moderately.

The study, "Anxiety and depression among abstainers and low-level alcohol consumers. The Nord-Trøndelag Health Study", was published in the most recent issue of Addiction, a peer-reviewed medical journal published by the Society for the Study of Addiction.

A long-standing mystery

Researchers have long struggled with a counterintuitive psychological mystery: While it's believable that heavy drinkers might be depressed, study after study shows that people who don't drink at all also have high levels of depression and anxiety. But why?

One working hypothesis has been that the depression recorded in groups that include teetotalers – people who don't drink at all -- may be due to the fact that these groups can include people who quit drinking because of alcoholism. If abstainers who quit drinking because it was a problem could be excluded from the larger group of non-drinkers, the results might be different.

A team from the Norwegian University of Science and Technology, the University of Bergen, a number of Norwegian public health organizations and Kings College, London set out to test this idea. The team used information from a questionnaire in which 38, 390 residents of a county in mid-Norway – fully 41 percent of the county's population -- described their general physical and mental health, along with typical alcohol use over a two-week period. The questionnaire was part of a larger, long-term study called HUNT, which has periodically examined the physical and mental health and well-being of the residents of Nord-Trøndelag county since 1984.

The researchers found that even when they removed people from the study who had quit drinking because of problems with alcohol, the general findings held true: heavy drinkers and non-drinkers are more likely to be anxious and depressed than those who drink moderately. All told, 17.3 per cent of abstainers reported anxiety, while 15.8 per cent reported depression.

The happiest people, in contrast, were those who averaged about two glasses of alcohol per week, where a glass of alcohol represents one bottle of beer, or a glass of wine, or a shot of strong spirits.

Solving the puzzle

The questionnaire also allowed researchers to determine the general health of respondents, which might explain the links between depression and alcohol intake.

"We found on average that there were more people with physical complaints among the non-drinkers than in the other groups", says Eystein Stordal, an adjunct professor at NTNU's Department of Neuroscience. "These individuals are more likely to use medicines that mean they shouldn't drink. But it may also be true that having such an illness increases a person's tendency to be anxious or depressed."

Researchers also found that non-drinkers reported having fewer friends than drinkers did, which might explain their increased odds of being depressed.

"We see that this group is less socially well-adjusted than other groups", Stordal says. "Generally when people are with friends, it is more acceptable in Western societies to drink than not to drink. While the questionnaire recorded non-drinkers' subjective perception of the situation, a number of other studies also confirm that teetotalers experience some level of social exclusion. "

Potential public health consequences

Nearly 12 per cent of the survey participants described themselves as abstainers, while another 22 per cent were non-consumers. Alcohol abstainers were also more often female and older, and reported more health problems than non-consumers and mid-range consumers.

The researchers noted that because abstinence is more common in Western societies compared to harmful drinking habits, the potential public health impacts of these findings could be great. "In the case of depression, the odds of depression (in people who labeled themselves abstainers) were higher than even the heaviest alcohol consumers," the authors wrote. "In a society where use of alcohol is the norm, abstinence might be associated with being socially marginalized and at increased risk for mental disorders."