Omega-3 fatty acids may prevent forms of depression associated with increased inflammation, according to a recent study.

People with increased inflammation, including those receiving cytokines for medical treatment, have a greatly increased risk of depression. For example, a six-month treatment course of interferon-alpha therapy for chronic hepatitis C virus infection causes depression in approximately 30 percent of patients.

Omega-3 fatty acids, more commonly known as fish oil, have a long list of health benefits, including lowering the risk of heart disease and reducing triglyceride levels. These nutritional compounds are also known to have anti-depressant and anti-inflammatory properties.

For the study, an international team of researchers recruited 152 patients with hepatitis C to participate, each of whom was randomized to receive two weeks of treatment with EPA, DHA, or placebo. EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are the two main omega-3 fatty acids in fish oil supplements.

Following the two-week treatment, the patients received a 24-week course of interferon-alpha treatment and were evaluated repeatedly for depression.

Researchers found that treatment with EPA, but not DHA or placebo, decreased the incidence of interferon-alpha-induced depression in patients being treated for hepatitis C.

"The study shows that even a short course (two weeks) of a nutritional supplement containing one such omega-3 polyunsaturated fatty acid (EPA) reduced the rates of new-onset depression to 10 percent," Carmine Pariante, senior author of the study, said in a statement.

In addition, both EPA and DHA delayed the onset of depression, and both treatments were well tolerated, with no serious side effects.

The results indicate that omega-3 polyunsaturated fatty acids may be effective in preventing depression in a group of patients at high-risk of depression because of increased inflammation.

The findings were published in the journal Biological Psychiatry.