The researchers believe that low consumption of omega-3 fatty acids found in oily fish contributes to depression, especially when combined with high consumption of omega-6 fatty acids found in nuts and processed food, The Melbourne Sun-Herald reports.

The How Food Affects Mood study is being conducted by the Australasian Research Institute at Sydney Adventist Hospital and the University of New South Wales. Scientists plan to recruit 1,000 teenagers ages 14 to 17, and to use dietary surveys and examination of their DNA.

Researchers say the ideal diet would have approximately the same amounts of omega-3 and omega-6 acids. But modern Australians tend to consume 15 times as much omega-6 because it is found in a greater variety of foods and especially in processed ones.