Several studies have shown an association between alcohol abuse or dependency and depression, but whether the two have a common cause or one causes the other has been unclear. Now a study suggests that alcohol abuse may actually be a cause of major depression.
Researchers from New Zealand examined data from a 25-year health and development study. Over 1,000 participants born in 1977 were assessed for both alcoholism and depression at ages 17 to 18, 20 to 21, and 24 to 25.
Alcoholism was present in 14 to 22 percent of the participants at various ages, and depression was present in 14 to 18 percent. At every age, those with alcoholism were twice as likely also to have major depression. The researchers also used three possible models to test the data; the one that was most plausible is that alcoholism led to depression.
Alcohol use could trigger genetic markers that increase the risk of depression; alcohol's depressant effect could lead to depression itself; or the stressful life circumstances alcoholism creates could lead to depression. These results are preliminary and do not agree with some previous studies, which have suggested that, in fact, depression leads to alcohol abuse or dependency. A number of models may be necessary to explain this complex relationship.
Source: Archives of General Psychiatry Volume 66, page 260, March 2009