Fatty fish, walnuts, and flaxseeds are all rich in a type of fat you can feel good about eating: omega-3 fatty acids. Not only does it help your body function properly, but it’s also associated with a number of health benefits, including lower levels of depression. Now, a new meta-analysis published in Translational Psychiatry suggests high-dose omega-3 supplements can have a positive impact on mental health, too.

"This new meta-analysis nuances earlier research on the importance of long chain omega-3s in [major depressive disorder] management,” lead author Dr. Roel Mocking, researcher at the program for mood disorders at the University of Amsterdam, said in a statement. Mocking and his team reviewed 13 studies involving a total of 1,200 participants with major depressive disorder in order to assess the effects of omega-3s on their symptoms. They also looked at whether or not these effects depended on the dose and ratio of two particular acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) — both of which are primarily found in fish.

DHA and EPA may be similar, but they each impact the body differently. For example, DHA is vital to brain and eye development, at the same time it works to help lower risk for heart disease. EPA, on the other hand, has been shown to reduce inflammation and depression levels.

The results showed omega-3 supplements did benefit those with major depressive symptoms; however, the benefits were greater in studies that used higher doses of EPA and in participants who were already taking antidepressants.

"Omega-3 supplements may be specifically effective in the form of EPA in depressed patients using antidepressants,” Mocking said. “This could be a next step to personalizing the treatment for depression and other disorders.”

Depression is one of the most common mental illnesses in the U.S., with an estimated one in 10 adults reporting the mood disorder. It’s marked by persistent feelings of sadness, misery, and loss of interest. According to the National Institutes of Mental Health, in 2014, nearly 16 million of U.S. adults aged 18 and older said they experienced at least one major depressive episode in the past 12 months.

That said, there is no universal treatment for depression. There are commonly prescribed methods, such as antidepressant drugs and cognitive behavioral therapy, to name a couple, but patient outcomes can vary. This gray area is where omega-3 supplements and foods may be most useful, according to prior research. Something as simple as a daily supplement could be huge for patients who have not responded to or found relief with traditional treatment.

Researchers concluded: “Additionally, this study underscores the importance of EPA and DHA omega-3s for overall health and well-being, and supports an existing body of research on the connection between omega-3s and depression.”

Source: Mocking R, Harmsen I, Koeter M, Ruhe H, Schene A. Meta-Analysis and Meta-Regression of Omega-3 polyunsaturated Fatty Acid Supplementation for Major Depressive Disorder. Translational Psychiatry. 2016.