MONTREAL – Omega-3 supplements have proven effective in treating depressed patients who do not also suffer from an anxiety disorder, a study involving Montreal researchers has found.

The study explored the effectiveness of fighting depression with Omega-3 supplements rather than anti-depressant drugs such as Prozac or Paxil.

“Many of these (alternative) treatments have not been adequately evaluated,” said Francois Lesperance, director of the study and head of psychiatry at the Universite de Montreal hospital centre.

A total of 432 participants in Quebec and Ontario took part in the four-year study. For eight weeks, half of the participants took three capsules a day of Omega-3 Emotional Balance, a fish oil supplement with high concentrations of EPA, the fats found in fish. The other half took three capsules of a placebo consisting of sunflower oil flavoured with fish oil.

At several stages during the eight weeks, participants were asked to fill out a questionnaire that evaluated their symptoms of depression.

“Overall, we found there was a small trend favouring Omega-3 over placebo, but it was not statistically significant,” said Nancy Frasure-Smith, a McGill University psychiatry professor involved in the study,

However, a subgroup of depressed patients who didn’t also suffer from an anxiety disorder saw their depression symptoms decrease after taking the Omega-3 supplements compared with those who took the placebo.

Other, smaller, studies have suggested that a deficit in polyunsaturated fatty acids of the Omega-3 group may predispose individuals to disorders such as depression.

The results of the Canadian study do not mean that depressed people will feel better if they eat large quantities of fish, which is high in Omega-3 fatty acids, researchers noted. The fish oil supplement used in the study had higher concentrations of Omega-3 than is available from an average diet.

Lesperance said it is difficult to study whether dietary intervention can prevent depression or other diseases, because these types of studies are complicated to carry out in a controlled setting.

He said a depressed patient who wants to try the supplements should first consult with their doctor.

This is the first large study examining the impact of Omega-3 supplements on depression. It was conducted by researchers at the Universite de Montreal, McGill, Queen’s and the Universite Laval.

The study was published this month in the online Journal of Clinical Psychiatry. About 70 per cent of the cost of the study was covered by the French firm isodisnatura, which manufactures the Omega-3 supplements.

In Canada, about 11 per cent of men and 16 per cent of women will suffer from depression at some point in their lives.