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 this group 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 a part of a long-term physical and mental health study of virtually all residents of Nord-Trøndelag County, called HUNT, which started in 1984. The questionnaire was conducted during HUNT's second phase, between 1995-1997.
The researchers found that even when they removed people from their study who had quit drinking because of problems with alcohol, the general findings held true: heavy drinkers and non-drinkers were 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.