New Canadian research suggests relatively cheap and safe fish oil might be a natural way to help lift mood in patients with some types of depression.

The study, published in the online Journal of Clinical Psychiatry, found that the essential fatty acids in fish oil can offer the same kind of relief that pharmaceutical medications offer.

The study was conducted by researchers in Montreal, Quebec City and Kingston, Ont. and looked at 432 male and female participants with major depression. The study included a high proportion of patients with complex and difficult-to-treat conditions, including patients resistant to conventional antidepressant treatments and patients also suffering from an anxiety disorder.

For eight weeks, half the participants were randomized to take three capsules per day of OM3 Emotional Balance, which contains about 1,000 mg of fish oil. The other half took identical capsules of a placebo, which contained sunflower oil flavoured with a small quantity of fish oil. Neither the patients nor researchers knew which capsules patients received.

At first, the researchers didn't notice any effects among the fish oil group. But when they eliminated depressed patients with anxiety disorders, they found that those patients taking the fish oil did benefit in the same way that those taking conventional antidepressant treatments usually do. That is: about two thirds of patients saw improvements in symptoms over the eight-week study period.

"It's a good effect, not a huge effect, but it's the same as you get with antidepressants," researcher Dr. François Lespérance of the University of Montreal explained to CTV News.

"We would have like to have seen the effect in all patients… we were happy we got this result."

Researchers think a component of the fish oils, called EPA (eicosapentaenoic acid) may have the key therapeutic effect, reducing the inflammation in the brain that could be the trigger for depression.

The study was funded in part by the European firm isodisnatura, which was the maker of the fish oil studied, OM3 Emotional Balance. It contains high concentrations of EPA.

While the study tested only the one brand, researchers believe other supplements with very high levels of EPA should have a similar effect.

The researchers say further studies are needed but they say that for patients diagnosed with depression, fish oil supplements with EPA are worth trying, especially in patients with hard to manage depression.

"We're happy to offer one more choice, among all other choices available for patients," said Lespérance.