Recent Findings on Omega-3s & Depression

Depression Affects Many Americans

Major depression (also called clinical depression) is a serious mood disorder that causes severe symptoms. Major depression is common according to the National Institute of Mental Health (NIMH). In 2014, roughly 15.7 million U.S. adults aged 18 or older had at least one major depressive episode in the past year.

Medically, a major depressive episode is defined as a period lasting 2 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.

Depression can also be mild or moderate. The mild form causes symptoms that can affect daily activities, though people continue to function – just not as well as they normally do. These symptoms are worse in moderate depression, and can cause real difficulties at home, work, and in social situations.

Omega-3 Fatty Acids and Depression

The omega-3s have been studied in depression, and the best evidence for their benefit has been seen in major and moderate depression. Several recent trials have shed some light on which of the omega-3s – EPA or DHA – may be more important, whether the omega-3s can make a difference for those already on antidepressant drugs, and how these fatty acids might be working to help stabilize mood.

More EPA or DHA for Depression?

A multinational research team recently performed a meta-analysis of 35 randomized clinical trials to better understand why some trials have found benefit of omega-3s in depression while others haven’t (1). Clinical benefits were seen in depressed patients given supplements containing predominately EPA (more than 50%), while supplements with higher DHA (>50% DHA) did not show benefits. DHA may be important too, but the benefits seem to depend more on the EPA content.

Omega-3s Boost Antidepressant Drug Effects

Antidepressant drugs can fall short for many people: A large-scale NIMH study found that less than 50% of people become symptom-free on antidepressants. Researchers from Harvard and the University of Melbourne recently conducted a review and meta-analysis of 40 clinical trials that looked at the ability of various nutrients to improve the response to anti-depressants when needed (2). While some nutrients like vitamin D and folic acid improved the response to common drugs (including SSRI and tricyclic drugs), the strongest effect was seen with fish oil omega-3s.

How Might Omega-3s Impact the Brain?

Fish oil may enhance white matter in regions of the brain that can be compromised in depression. White matter consists of myelinated fibers that connect brain cells. Myelin, made of protein and fats, covers many nerve fibers to boost the speed at which they conduct impulses.

Since blood levels of the omega-3s can be low in major depression and these fatty acids affect myelination, Columbia University researchers theorized that fish oil might help ease depression by improving the structural integrity of white matter.

To test this theory, patients with severe depression underwent brain imaging before and after 6 weeks of fish oil supplementation (3). Eighty percent of those whose depression improved with fish oil had increased white matter in important brain areas, while an increase was seen in only 45% of those who didn’t respond to the supplement. These findings offer one explanation for how omega-3s help combat depression along with their inflammation-fighting actions.

References:

1. Hallahan B, et al. Efficacy of omega-3 highly unsaturated fatty acids in the treatment of depression. Br J Psychiatry [Epub ahead of print] April 21, 2016.
2. Sarris J, et al. Adunctive nutraceuticals for depression: a systematic review and meta-analyses. Am J Psychiatry [published online April 26, 2016].
3. Chhetry BT, et al. Omega-3 polyunsaturated fatty acid supplementation and white matter changes in major depression. J Psychiatr Res 75:65-74, 2016.