In a surprise and not very welcome finding, researchers report that fish oil supplements do not ease depression in individuals who suffer from both depression and coronary heart disease.
Participants in the study, which is published in the Oct. 21 issue of the Journal of the American Medical Association, were also taking the antidepressant sertraline (Zoloft). Some studies have suggested that the omega-3 fatty acids found in fish might enhance the effects of Zoloft.
"Unfortunately, it's not where we wanted to be. We were kind of disappointed, to say the least," said study author Robert M. Carney, a professor of psychiatry at Washington University School of Medicine in St. Louis.
The findings leave physicians still facing the problem of how to boost depression recovery rates so as to also lower cardiovascular risk. The question is a pressing one, given that depression can double or even triple the risk of dying in heart patients, Carney said.
"We're not just treating depression, we're treating a risk factor," he said.
Fish oil, or omega-3 fatty acid, supplements have been touted as a potential panacea for a variety of ailments, notably heart disease, but they have been losing their luster as of late.
A study published earlier this year found that patients receiving optimal drug therapy after experiencing a heart attack do not gain any additional benefit from taking supplemental omega-3 fatty acids. There was no difference in rates of heart attack, stroke, sudden cardiac death or death from any cause, regardless of whether they were taking the supplements or not.
That finding contradicted previous studies, which suggested that taking omega-3 fatty acids improved long-term survival.
Studies involving omega-3 fatty acids and depression have shown similarly uneven results.
For this study, 122 patients with major depression and coronary heart disease took 50 milligrams of Zoloft a day, then were randomized to receive either 2 grams a day of omega-3 acid ethyl esters or a corn-oil placebo capsule.
There was no difference in depression scores before and after 10 weeks of treatment, the researchers found.
The study authors noted that tweaking any of the variables in the study -- amount of Zoloft, dose of fish oil, form of fish oil or duration of treatment -- might yield more positive results.
In general, the effects of antidepressants in people with both depression and heart problems are the same as in a normal "healthy" population, Carney said.
"The problem, from our point of view, is that that's just not good enough," he added. "It's definitely better than placebo, better than doing nothing. We're trying to find a treatment or combination of treatments that's going to significantly improve the depression outcome."
Had this study turned out more positively, the next step would have been to see if improvements in depression translate into improvements in heart outcomes.
As it is, scientists are back to the drawing board.
"We're still exploring other possibilities," Carney said.
That includes an increased dose of omega-3, lengthening the study and identifying a subset of patients for whom this protocol might be more effective than antidepressants alone.
But it's not time to stop taking fish oil capsules yet, one expert said.
"The American Heart Association still does have recommendations based on the data we do have," said Dr. John Erwin III, professor of internal medicine at Texas A&M Health Science Center College of Medicine, and senior staff cardiologist with Scott & White Hospital in Temple.
"We also use fish oil to reduce triglyceride levels and it's very effective in that use. I wouldn't encourage people who are taking fish oil caplets to stop it now because of this study. It just means we have a little bit more work to do on the depression side of things," he said.
Some of the study authors, including Carney, declared financial ties with different pharmaceutical companies including Pfizer Inc., which makes Zoloft. The study was funded by the U.S. National Heart, Lung, and Blood Institute. GlaxoSmithKline Inc. provided both omega-3 and placebo capsules, while Pfizer supplied the Zoloft.
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