Fish Oil Helps Treat Depression

Aug. 19 -- — For years, researchers have been searching the seas, collecting rare sponges, coral and algae in the hope that the chemicals they contain might become potent medications.

Now some researchers say they've found an effective antidepressant below the waves: Fish, or more specifically, fish oil containing so-called omega-3 fatty acids.

"We've been very impressed by the response rates we've observed," said Dr. David Mischoulon, a psychiatrist at Massachusetts General Hospital who has overseen an omega-3 clinical trial. "We believe there is definitely something to these treatments."

Scientists first became interested when they noticed that countries with the highest fish consumption had the lowest rates of depression. They also observed that mothers in England who ate very little fish during pregnancy doubled their risk of developing postpartum depression compared to women who ate fish regularly. So scientists began a series of studies to see why.

Omega-3 Fatty Acids Found to Have Same Effect

Researchers found that omega-3 fatty acids, when fed to piglets, had the same effect on the brain as the antidepressant Prozac: They raised levels of a critical neurotransmitter, serotonin.

"After only 18 days, those animals that were fed the enriched formula had double the level of serotonin in their frontal cortex, in the part of the brain that regulates depression and impulsivity," said Dr. Joseph Hibbeln, a senior clinical investigator at the National Institutes of Health.

Omega-3 fatty acids are polyunsaturated oils that cannot be made by the body and are derived primarily from seafood. The fatty acid with most direct influence on brain development and function is DHA.

"The DHA is highly concentrated in the brain," Hibbeln told ABCNEWS, "and it's concentrated in the brain right where the neurons communicate with each other and all the signals pass back and forth."

The DHA from omega-3 makes up the walls of neurons, Hibbeln said. "The body cannot manufacture DHA so it has to get it from our diet."