Researchers say there is not enough high-quality evidence to suggest omega-3 supplements can help treat depression.
Omega-3 fatty acids are found naturally in oily fish, including tuna and seafood, as well as in some nuts and seeds.
Omega-3 is also available as a dietary supplement, and it has become one of the most popular nutritional supplements in the US in recent years - largely due to studies hailing its health benefits, such as reduced risks for heart disease and improved cholesterol.
More recently, studies have suggested omega-3 supplementation may help treat major depressive disorder (MDD) - a condition that is estimated to affect around 6.7% of adults in the US every year, with women most at risk.
Dr. Katherine Appleton, from Bournemouth University in the UK, and other members of Cochrane - a global independent network of researchers and health professionals - set out to assess this association further, reviewing 26 randomized trials involving a total of 1,458 participants.
They recently published their findings in the Cochrane Library.
Modest effect identified 'unlikely to benefit patients with depression'
Each trial looked at how omega-3 supplements compared with a placebo for treating major depression, and one study - involving a total of 40 participants - also compared the effect of omega-3 against antidepressant medication.
Fast facts about depression
- The average age of MDD onset in the US is 32
- Women are 70% more likely to develop MDD than men
- Around 3.3% of adolescents aged 13-18 in the US have experienced a severely debilitating depressive disorder.
Compared with participants who took placebos, the researchers found that those who received omega-3 supplements had lower symptom scores for major depression. However, they found that the effect was minimal and identified a number of limitations that hampered confidence in the results.
"We found a small-to-modest positive effect of omega-3 fatty acids compared to placebo, but the size of this effect is unlikely to be meaningful to people with depression, and we considered the evidence to be of low or very low quality," explains Dr. Appleton.
"All studies contributing to our analyses were of direct relevance to our research question, but most of these studies are small and of low quality," she continued.
Based on their findings, the Cochrane authors conclude that there is insufficient evidence to suggest omega-3 supplementation is an effective treatment for MDD.
Dr. Appleton adds:
"At present, we just don't have enough high-quality evidence to determine the effects of omega-3 fatty acids as a treatment for major depressive disorder. It's important that people who suffer from depression are aware of this, so that they can make more informed choices about treatment."
Earlier this year, Medical News Today reported on a study published in Nature Communications that suggested taking omega-3 supplements for 12 weeks may reduce the risk of developing schizophrenia and other psychotic disorders.