Some depressed patients are treatment-resistant — their symptoms do not lessen no matter what drug they take. Interestingly, given an anti-inflammatory drug, such patients who also happen to have high inflammation levels will find relief from their symptoms of depression. Now, a new study takes this unusual finding one step further — people with both depression and high inflammation benefit from taking omega-3 fatty acid EPA (eicosapentataenoic acid).

Your body uses inflammation as a defense to protect against disease or infection. While you probably recognize inflammation when your sprained ankle begins to swell, you may not understand that your brain also can become inflamed. Though this natural response may be healing, too much inflammation can be damaging.

A link between depression and inflammation was established earlier this year. After scanning the brains of 20 patients with depression and 20 healthy participants, a research team observed significant inflammation in the brains of people with depression. In fact, symptom severity directly related to inflammation levels — the patients with major depression showed a 30 percent inflammatory increase.

New Mood Booster?

For the current study, scientists from Emory and Harvard Universities enlisted the help of 155 participants diagnosed with major depression, the most severe form of this mood disorder. The study began with the researchers measuring four inflammation biomarkers in each participant and then placing each into a low or high inflammation group. Then, the researchers randomly assigned participants to receive either 1,060 mg of EPA or 900 mg of docosahexaenoic acid (DHA), or a placebo daily over an eight-week period. EPA and DHA are different types of omega-3 fatty acids, essential nutrients which originate in microalgae.

At the end of the eight-week period, the researchers assessed each participant’s level of depression. The "high inflammation" subjects improved more with EPA than with either placebo or DHA.

This finding suggests anti-inflammatory treatments might be effective in specific subgroups of patients with depression, the researchers say. Even more, the results support the theory that anti-inflammatory therapy is only beneficial in treating inflammation-driven major depressive disorder, while possibly presenting harm to those who suffer from depression caused by a different physiological disturbance.

For this reason, the researchers advocate evaluating a depressed patient’s inflammation status to identify those who might respond to treatment with EPA. Additional studies are needed, the researchers wrote, “to replicate and extend this proof-of-concept work.”

Source: Rapaport MH, Nierenberg AA, Schettler PJ, et al. Inflammation as a predictive biomarker for response to omega-3 fatty acids in major depressive disorder: a proof-of-concept study. Molecular Psychiatry. 2015.