New research out today concludes that there is insufficient evidence for the use of taking an Omega 3 fatty acid supplement in treating major depressive disorder.

Omega 3 fatty acids are widely thought to be essential for good health and are naturally found in fatty fish, such as tuna, seafood and some nuts and seeds.

Omega 3 fatty acids have been widely promoted globally and are readily available, over-the-counter supplement. These supplements have hugely increased in popularity over the last decade together with a range of other supplements including ginseng, garlic, green tea, as well as vitamins, minerals and herbal products.

More recently there have been various studies that have suggested a role for Omega 3 fatty acid supplementation in treating major depressive disorder. Adults with major depressive disorders are characterized by depressed mood or a lack of pleasure in previously enjoyed activities for at least two weeks, in the absence of any physical cause, that impact on everyday life.

Figures published by the World Health Organization in 2011 estimated major depressive disorders to account for 3% of global ill health and projections for 2030 suggest an increase to 6% or 7%.

A new Cochrane review, published today in the Cochrane Library, gathered together data from 26 randomized trials involving a total of 1,458 participants. The trials investigated the impact of giving an Omega 3 fatty acid supplement in a capsule form and compared it to a dummy pill. In one study, involving 40 participants, they also investigated the impact of the same supplementation compared to an anti-depressant treatment.

The Cochrane authors found that whilst people who were given Omega 3 fatty acids reported lower symptom scores than people with the dummy pill, the effect was small and there were important limitations that undermined their confidence in the results. Their analyses showed that although similar numbers of people experienced side effects, more data would be required to understand the risks of taking Omega 3 fatty acids.

Lead author, Katherine Appleton from Bournemouth University said, "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. 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 added, "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."