A meta-analysis conducted on 9 studies showed mixed findings on the efficacy of omega-3 polyunsaturated fatty acid (n-3 PUFA) supplements in reducing depressive symptoms among adults over 60. In identifying specific moderating effects, however, dosage over 1.5 g/day of n-3 PUFA compared with placebo was found to reduce depression in an older population, according to a study published in the Journal of Affective Disorders.
Relevant electronic databases were searched for eligible studies from their inception through June 4, 2018, including MEDLINE, EMBASE, Web of Science, Cochrane Library, PsycINFO, Global Health databases, CINAHL, ClinicalTrials.gov, and the Chinese Biomedical Medicine Database. Data were extracted and assessed from 9 randomized controlled trials that met specific inclusion criteria: participants aged 60 and up, interventions consisting of n-3 PUFAs without other depression treatment, comparison groups receiving placebo, and symptoms measured by depression rating scales as the main outcome. Moderator analyses were used to highlight factors that influence variability of effect size, including dosage, baseline depression, intervention duration, comorbidities, and ratio of eicospentaenoic acid and docosahexaenoic acid in the n-3 PUFA supplement composition.
Study results showed n-3 PUFA supplements reduced depressive symptoms in older adults; however, the differences between n-3 PUFA and control conditions were found to be statistically nonsignificant in treating depressive symptoms. Meta-regression analyses found that interventions with n-3 PUFA dosage greater than 1.5 g/day had a statistically significant effect size of -0.428 (95% CI, -0.822 to -0.035). Researchers did not find significant moderating effects on depression symptoms associated with intervention duration, baseline depression, comorbid disease, or the eicospentaenoic acid to docosahexaenoic acid ratio.
A limitation of using only 9 studies provided limited statistical power for moderator analysis, which typically requires the inclusion of least 20 studies; therefore, the results of this review are suggestive. A second limitation was that researchers only reviewed studies published in English or Chinese, potentially causing study selection bias.
The present study found n-3 PUFA treatment with dosage greater than 1.5 g/day effectively reduced depressive symptoms in older adults. Besides dosage, meta-regression analyses did not find other moderating effects significant on depressive symptoms. Further randomized controlled trials that are high in quality and have large cohorts are needed to confirm current conclusions.
Bai ZG, Bo A, Wu SJ, Gai QY, Chi I. Omega-3 polyunsaturated fatty acids and reduction of depressive symptoms in older adults: A systematic review and meta-analysis [published online July 27, 2018]. J Affect Disord. doi: 10.1016/j.jad.2018.07.057.