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Omega-3 may help depression caused by certain types of inflammation

Fish oil capsules photo via Pexels

The omega-3 fatty acid EPA (eicosapentataenoic acid) appears to boost mood in a subgroup of patients with major depressive disorder (MDD) who have high inflammation levels, researchers found in a study published in the journal Molecular Psychiatry,


Previous studies have shown that dietary supplementation with the long-chain omega-3 fatty acids found in fish oils can be effective as an add-on treatment for clinical depression for at least some patients with this condition, many of whom are not helped by standard treatments.

However, depression is not a unitary condition, as the contributory factors (as well as the actual clinical symptoms) can vary widely between individuals.  Both researchers and clinicians have therefore long tried to identify particular subgroups, and find reliable biomarkers, which can help improve treatments for this condition. 

The findings from this new study are helpful in two ways, as:
1) they strengthen the existing evidence that EPA, not DHA, is the omega-3 most effective for reducing depressive symptoms. See: 

2) they also support previous suggestions that biomarkers of inflammation may help predict a good response to EPA treatment.

Excessive inflammation is characteristic of many (but not all) patients with depression, and omega-3 EPA has long been known to have
powerful anti-inflammatory effects.

(EPA could also potentially provide a safer alternative as an adjunctive treatment for depression than anti-inflammatory medications, which can have adverse side-effects, as the researchers note).

For details of this study, please see:

And for more information on this subject, please see the following lists of articles, which are regularly updated:

In a randomized trial, 155 participants were given either two capsules containing EPA-enriched mix or a placebo, or four capsules of a DHA (docosahexaenoic acid)-enriched mix or four placebo capsules for eight weeks. All participants were previously diagnosed with major depressive disorder.

EPA was found to be effective for a group of patients who had high levels of at least one of four markers of inflammation in their blood. DHA was not effective for this group of patients.

The authors call the finding a proof-of-concept for the idea that anti-inflammatory treatments can be effective in subgroups of patients with depression.

This goes along with earlier studies showing that an anti-inflammatory drug infliximab can be effective in some patients with treatment-resistant depression, specifically those with high levels of inflammation.

According to the authors, these results support the proposition that anti-inflammatory therapy is only beneficial as a treatment of inflammation-driven major depressive disorder, and is ineffective and potentially harmful for individuals whose depression is due to a different physiological disturbance.

The authors go on to say they have preliminary data suggesting that obese patients with depression are more likely to have high markers of inflammation, and might benefit from anti-inflammatory drugs. In future studies, they are going to replicate their preliminary findings and extend them by investigating the influence of other important biological measures and clinical characteristics.