Doctors in one review said that prior studies revealed a link between abnormal fatty acid levels and increased chances of major depression. Researchers analyzed 28 depression studies that measured omega-3s and depressive symptoms. They found that EPA (eicosapentaenoic acid) in particular had a significant anti-depressant effect. Also, scientists found that omega-3 supplements were more effective in treating bipolar and major depression rather than milder forms.
Doctors believe that supplementing with omega-3s, and specifically with EPA, helps normalize fatty acid levels, reducing symptoms of major depression.