Teenage Depression - Fish Theory to be Tested

SCIENTISTS believe the mood of teenagers could be determined by the food they eat - and are about to put their theory to the test.

A group of Australian scientists believe too few omega-3 fatty acids, found in fish and seafood, and too many omega-6 fatty acids, found in processed oils and nuts, raises the risk of depression in adolescents.

Up to 1000 Sydneysiders aged 14 to 17 will be recruited for the biggest study of its kind on whether adolescents truly are what they eat.

Lower seafood consumption has been linked to higher rates of depression in adults. The study will attempt to prove it affects teenagers in the same way.

The How Food Affects Mood study, by the Australasian Research Institute at Sydney Adventist Hospital and the University of NSW, will use DNA testing from cheek swabs and dietary surveys.

Researchers want to know if an imbalance in levels of omega-3 and omega-6 - due to increases in processed foods - heightens the probability of depression.

Humans evolved with a diet equal in both essential fatty acids but current Western diets have up to 15 times more omega-6 than omega-3.

Omega-3 fatty acids are critical to brain development and function, but because our bodies cannot effectively make them we rely on dietary sources.

However, most Australians consume less than a quarter of the optimal recommended intake because it is only found in a few foods, including oily fish such as salmon and sardines.

Previous NSW research showed children need to eat five times more fish and seafood than they do.

The study will be the first to measure which variant a teenager has of the serotonin transporter gene, which is responsible for our uptake of "feel-good" serotonin and mood control.

In 2006 Australian research found people who carry a "short" version of the gene tend to be more susceptible to depression, while those with the "long" version are more resilient against negative life events. The institute's Dr Ross Grant said the results would be used to give teenagers positive messages about healthy eating. "Often kids who are physically unhealthy are emotionally unhealthy as well," he said.

Co-researcher Margaret Morris said dietary intervention could ultimately be used to prevent and treat mood disorders.

"If there is a causal link between omega-3, serotonin transporter genotype and depression, we can develop better strategies to deal with it," she said.