The causal relation is not vice versa

Mar 3, 2009 12:03 GMT  ·  By

Since alcohol abuse has first been tied to depression, doctors have thought that it's the latter that makes people pick up drinking, on account of the fact that depression has been believed to be caused by factors independent of beverages. Now, according to a new batch of studies, the opposite seems to be true, in that people who were not depressed before they started consuming alcohol ended up showing the symptoms of the condition. The finds are published in the March issue of the scientific journal Archives of General Psychiatry.

“The underlying mechanisms that give rise to such an association are unclear; however, it has been proposed that this link may arise from genetic processes in which the use of alcohol acts to trigger genetic markers that increase the risk of major depression. In addition, further research suggests that alcohol's depressant characteristics may lead to periods of depressed affect among those with alcohol abuse or dependence,” the authors of the new paper, led by University of Otago Christchurch School of Medicine and Health Sciences researcher David M. Fergusson, PhD, write. The team is based in Christchurch, New Zealand.

“This analysis suggested that the best-fitting model was one in which there was a unidirectional association from alcohol abuse or dependence to major depression, but no reverse effect from major depression to alcohol abuse or dependence,” they add. The team has looked into several models that could explain the associations between alcohol and depression, and has learned that there are, indeed, no other external factors to influence both at once, as previous studies have suggested.

For the new research, the scientists have used data from a 25-year-long study of health and development in the country, and have analyzed the cases of 1,055 participants. The subjects were tracked for three time intervals – between the ages 17 and 18, 20 and 21, as well as between 24 and 25. In addition to the depression- and alcohol-related questions, they were also asked about their lifestyles and about the socioeconomic factors that most influenced their lives.

The research results have shown that there certainly is no direct causal effect to lead depressed people to pick up alcohol drinking. On the other hand, those who consumed large amounts of alcohol showed the clear signs of the condition, without having outside factors influencing their mood in any way. They started exhibiting sleep disorders and other such behavior, which has led scientists to conclude that people should consume alcohol moderately, so as to avoid getting depressed in early adulthood and later on in life.