— 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."
At Sheffield University in England, Dr. Malcolm Peet gave omega-3 fatty acids to 70 depressed patients who had not been helped by drugs such as Prozac. After 12 weeks, 69 percent of the patients showed marked improvement compared with 25 percent given placebos.
Trial Participant Accounts Significant Improvement
Jim LaBonte of Boston took part in another omega-3 study. LaBonte, who was diagnosed with depression four years ago, had tried Prozac but didn't like the way it made him feel. He complained the drug left him with no emotions, and so he stopped taking it. Then he enrolled in a clinical trial at Massachusetts General Hospital.
"I leaned more toward the skeptical. I wanted to say, 'show me,' " LaBonte told ABCNEWS.
LaBonte took the omega-3 fatty acid DHA each day. Within three weeks, he said, he noticed a significant improvement. He has now been taking DHA for eight months.
"I'm fine today. Not only do I not feel as blue, but when they [depressed feelings] do come I am able to handle it," he said.
"We're confident that the results he had were positive," said Mischoulon. "We've also observed similar responses in other people. So it's pretty clear in our minds that these treatments work."
Preliminary studies suggest 1 gram a day of omega-3 fatty acids can be an effective treatment, whether in the form of a nutritional supplement available at most health-food stores or simply by eating fish — especially salmon, sardines or tuna — several times a week.
Researchers say much larger studies are now needed to follow up on the initial success of omega-3 trials, not only against depression but also in treating schizophrenia, bipolar disorder, and violent behavior.