Researchers have found that certain fatty acids, including omega-3, work better to reduce symptoms of depression in people with higher signs of bodily inflammation, compared to people without those signs. This finding supports the use of fatty acids to treat some people with depression.

Appearing online March 24th in Molecular Psychiatry, the research was led by three NARSAD-funded scientists: Mark H. Rapaport, M.D., a 1999 Independent Investigator Grantee; Andrew A. Nierenberg, M.D., a Scientific Council member, 2000 and 2003 Independent Investigator Grantee, 2013 Distinguished Investigator Grantee, and winner of the Foundation’s Colvin Prize in 2013; and David Mischoulon, M.D., Ph.D., a 1998 and 2000 Young Investigator Grantee. Dr. Rapaport is from the Department of Psychiatry and Behavioral Sciences at Emory University School of Medicine, and Drs. Nierenberg and Mischoulon are from the Depression and Clinical Research Program at Massachusetts General Hospital.

The study focused on omega-3 fatty acids, which are found in some green vegetables, vegetable oils, and fatty fish. Omega-3 fatty acids are recommended as a way to protect against heart disease and stroke. In this study, people with major depressive disorder were given one of two omega-3s: eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA). They were also tested to see whether they had any of 10 chemicals in their blood indicating high inflammation levels. People with one or more indicators of high inflammation showed a greater reduction in depressive symptoms if taking EPA compared DHA, relative to people taking placebos (look-alike pills with no active ingredients). People who showed no indicators of high inflammation responded less to EPA than either DHA or placebo. The different effects of each omega-3 may stem from EPA’s stimulation of anti-inflammatory chemicals in the body––chemicals that DHA does not stimulate.

These findings point to positive and negatives for anti-inflammatory treatment of depression. On the positive side, omega-3s such as EPA with anti-inflammatory properties may help relieve symptoms in people whose depression is associated with high inflammation levels. This link is common among obese people with major depressive disorder. On the negative side, such omega-3s may actually interfere with treatment for those whose depression is associated with different physical traits.

The researchers also found that the presence of multiple rather than singular indicators of inflammation better predicted whether EPA would help them. Future work, they say, should build on this relatively small-scale study by continuing to look at more than one inflammatory marker when trying to personalize depression treatment based on inflammation levels.

Read the abstract.