Many studies have shown a heritable component to depressive disorders, but a specific cause has not been identified. Recently, scientists in two separate studies located a specific chromosomal region that is associated with depression.

Both studies were recently published in the American Journal of Psychiatry. One study was led by a team at Washington University in St. Louis and evaluated families who had diagnoses of major depressive disorder (MDD). In all, there were 91 Australian families with two or more siblings with MDD and 25 Finnish families with siblings affected with MDD. The second study, conducted primarily in the United Kingdom, evaluated 839 families with siblings pairs diagnosed with severe recurrent MDD. In a rare scientific occurrence, both studies reported that the same gene was associated with MDD, a region on chromosome 3 known as 3p25-26.

Replication of findings like this usually takes years, especially in genome-wide studies, if it is ever accomplished at all. The fact that both research teams simultaneously replicated each other’s findings is astounding — and promising. Researchers and clinicians alike hope that this new evidence will prompt new gene-based therapies to treat depression. Currently available medications for depression are only effective in about half of patients.

Previous studies of depression have indicated that depressive disorders are influenced by genetics, environmental factors, and external factors, and the interactions among them. The genetic component likely accounts for a little less than half of the risk of developing depression. Many genes are involved, in addition to 3p25-26. Further studies are necessary to identify more genes, and external factors, that influence depression.

MDD affects nearly 20% of people at some point in their lives. It is a costly and potentially debilitating condition. Personalized and individualized pharmacotherapy and psychotherapy are the cornerstones of the successful treatment of depression. Each piece of evidence that points to an identifiable cause of this disorder is one step closer to more effective treatment options.

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