Previous studies into fatty acids and depression have measured omega-3 levels in the blood of depressed humans, giving rise to the 'phospholipid hypothesis', which proposes that decreased omega-3 fatty acid intake (and hence decreased brain omega-3 fatty acid content) could be responsible for the disease.

Now researchers from Ben Gurion University of the Negev in Israel have reported for the first time that omega-3 fatty acids could also help children suffering from depression, a condition that “may be more common than previously thought”.

According to the US Department of Health and Human Services, as many as one in every 33 children may suffer from clinical depression, while the statistic in adolescents could be much higher – one in eight.

The researchers, led by Professor Haim Belmaker, randomly 28 depressed children, aged between 6 and 12, to receive either an omega-3 fatty acids or placebo for one month. Twenty of the children completed the study.

The omega-3 supplement was “a combination of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) that is commonly available as an over-the-counter preparation.”

Depression scores of the children was measured at the start of the trial and then again after two, four, six, eight, 12 and 16 weeks. Three scales were used to quantify the level of depression: Children's Depression Rating Scale (CDRS); Children's Depression Inventory (CDI); and Clinical Global Impression (CGI).

At the end of the trial the researchers found that seven out of ten children in the omega-3 group and none of the children in the placebo group had depression score reductions of 50 per cent or more.

Belmaker and his colleagues report in the American Journal of Psychiatry (Vol 163, pp. 1098-1100) that four of the children taking the omega-3 supplements achieved remission.

“Omega-3 fatty acids may have therapeutic benefits in childhood depression,” concluded the researchers.

The mechanism behind the supplement's effect on cognitive function seems to be specific to the type of omega oil. DHA is said to be involved in the membrane of ion channels in the brain, making it easier for them to change shape and transit electrical signals.

EPA is proposed to function by increasing blood flow in the body. It is also suggested to affect hormones and the immune system, both of which have a direct effect on brain function.