Fish has long been hailed as brain food. Now, it turns out, fish oil is also beneficial in treating brain illnesses, such as depression.

In a study published in the journal Molecular Psychiatry, Emory University researchers found that the omega-3 fatty acid EPA (eicosapentataenoic acid) can boost the mood of patients with major depression, Medical Xpress reports.

The study involved 155 depression patients who were given either two capsules containing EPA or a placebo, or four capsules of the omega-3 fatty acid DHA (docosahexaenoic acid) or four placebo capsules for eight weeks.

The results showed the EPA effectively reduced depressive symptoms more than the other pills and also lowered at least one of four biomarkers of inflammation in their blood tied to depression.

The authors call the finding a "proof-of-concept" for the idea that anti-inflammatory treatments can be effective in some patients with depression.

"The diversity of both symptoms and underlying variations of the progression of major depressive disorder confounds the development of targeted treatments for the disease," said lead researcher Mark Hyman Rapaport, M.D., a professor and chair of the Department of Psychiatry and Behavioral Sciences at Emory University School of Medicine.

"The discovery of biomarkers that characterize subgroups of patients with [major depression] is critical to the understanding of its pathogenesis, and to the development of personalized therapies."