Findings from Spain and Taiwan add evidence that omega-3s can deter depression
by Craig Weatherby
Earlier this year, a panel appointed by the American Psychiatric Association (APA) concluded that people who consume lots of omega-3s from fish and fish oil (EPA and DHA) are substantially less likely to suffer from depression, bipolar disorder (manic-depression), and related mood disorders.
As the panel wrote, “EPA and DHA appear to have negligible risks and some potential benefit in major depressive disorder and bipolar disorder …” They concluded that the benefits of omega-3s were much less clear with regard to reducing the risk or severity of schizophrenia and various personality disorders (Freeman MP et al 2006).
(For the full story, see” Top Psych Panel Says Omega-3s Deter Depression, Bipolar Disorder”.)
Two studies published over the summer add more support for the hypothesis that omega-3s are important to mood and mental health.
The first, published in July of this year by Taiwanese researchers, was a “meta-analysis”, which analyzed the best published clinical trials and tried to draw conclusions about overall trends in the evidence.
The second study, published just a month later by Spanish scientists, was a large “prospective cohort study”—the type that follows a group of people over time, recording their diets and health status at the beginning and end.
Let's take a look at the outcomes of each investigation.
Taiwanese review finds omega-3s deter depression
Researchers at two Taiwanese universities reviewed the results of clinical trials that tested omega-3s for their anti-depressant effects.
They selected only well-designed studies that lasted a month or more and were published in English. These criteria led them to 10 double-blind, placebo-controlled studies in patients with mood disorders.
After analyzing the 10 studies—which involved 329 participants in all—they concluded that "our meta-analysis showed significant antidepressant efficacy of omega-3s…” which "significantly improved depression in patients with clearly defined depression… or bipolar disorder” (Lin PY, Su KP 2007).
As with many meta-analyses, the researchers cautioned that their findings were limited by differences in study design, which made it difficult to compare the results of the 10 clinical trials in an apples-to-apples fashion.
Accordingly, they issued a call for more large-scale, well-controlled trials to pinpoint the levels and proportions of the two major omega-3s in fish oil—DHA and EPAmost effective in preventing and treating depression and bipolar disorder in specific subgroups of patients.
While EPA is sometimes presumed to be the more promising marine omega-3 with regard to mood disorders, the Taiwanese found no significant link between the amount of EPA that participants received and “the antidepressant efficacy” of fish oil in the clinical trials they analyzed.
Spanish study finds daily fish habit cuts depression risk by one-third
Researchers at the University of Las Palmas de Gran Canaria in Spain set out to redress the scarcity of large population studies assessing the ability of omega-3s to deter psychiatric disorders.
They enrolled 7,903 participants for a “prospective cohort” study, in which they followed a group of volunteers for two years and ascertained their omega-3 intake and fish consumption with a diet questionnaire.
After two years, they examined the participants for signs of depression, anxiety, or severe stress.
They then separated the subjects in five groups (quintiles) – categorized according to their self-reported omega-3 and fish consumption – and looked at the incidence of depression, anxiety, or severe stress in each group.
The risk of depression, anxiety, and stress declined as omega-3 intake rose:
- Participants reporting the highest omega-3 intake were least likely to show signs of depression, anxiety, or stress;
- Participants reporting the lowest omega-3 intake were most likely to show signs of depression, anxiety, or stress;
To put this in perspective, the volunteers who reported fish consumption in the middle of the range (112 grams or 4 oz per day) were 30 percent less likely to show signs of depression, anxiety, or stress.
As the Spanish team concluded, in typically dry scientific terms, “A potential benefit of w-3 PUFA intake on total mental disorders is suggested…” (Sanchez-Villegas A et al 2007).
One wonders when psychiatrists will try prescribing this widely beneficial nutrient before jumping to prescribe marginally effective synthetic drugs… pharmaceutical “blunt instruments” with known (and unknown) side effects and drug interactions.
- Lin PY, Su KP. A meta-analytic review of double-blind, placebo-controlled trials of antidepressant efficacy of omega-3 fatty acids. J Clin Psychiatry. 2007 Jul;68(7):1056-61.
- Sanchez-Villegas A, Henriquez P, Figueiras A, Ortuno F, Lahortiga F, Martinez-Gonzalez MA. Long chain omega-3 fatty acids intake, fish consumption and mental disorders in the SUN cohort study. Eur J Nutr. 2007 Aug 23; [Epub ahead of print]