A regular dose of omega-3 fatty acids can relieve symptoms for people suffering from major depressive disorder (MDD)—so says a meta-analysis of 13 scientific studies, including 1,233 participants, published in 2016 in Translational Psychiatry.

The analysis found that omega-3s delivered benefits to most participants but yielded the best results if the following two criteria were met: 1) The omega-3 supplement contained a higher ratio of eicosapentaenoic acid (EPA) to docosahexaenoic acid (DHA); and 2) The person had actual MDD versus just some depressive symptoms. Researchers also found that omega-3s helped even when taken in conjunction with antidepressant medications.

MDD affects about 7 percent of American adults, according to the National Institute of Mental Health. The Institute defines a major depressive episode as: “a period of two weeks or longer during which there is either depressed mood or loss of interest or pleasure, and at least four other symptoms that reflect a change in functioning, such as problems with sleep, eating, energy, concentration and self-image.”