Effect of Long-term Supplementation With Marine Omega-3 Fatty Acids vs Placebo on Risk of Depression or Clinically…
The largest trial ever run found fish oil did not prevent depression and if anything nudged the risk slightly up — am I taking it for prevention, and if so is there any reason to keep going?
Top of the evidence hierarchy, independently funded. how we score evidence
Caveat on this rating: The higher depression rate was a borderline result on one of two coprimary outcomes while the other (mood scores) showed nothing at all; the authors did not claim omega-3 causes depression, and this was a prevention trial in people without clinically relevant depressive symptoms at baseline, so it does not test omega-3 as a treatment for existing depression. Study capsules and matching placebo were donated by Pronova BioPharma, an industry in-kind contribution, though the trial itself was NIH-funded, the funders had no role, and the result was unfavourable to the product.
Fish-oil, EPA and DHA products sold for mood are dietary supplements under DSHEA: no FDA review of safety or effectiveness happens before they go on sale, and none is approved to treat depression or any other psychiatric condition. Prescription omega-3 drugs do exist, but for lipids, not mood.
In 18,353 US adults aged 50 and older randomised to 1 g/day of marine omega-3 (465 mg EPA plus 375 mg DHA) or matching placebo for a median 5.3 years, omega-3 did not prevent depression: depression or clinically relevant depressive symptoms occurred at 13.9 per 1,000 person-years on omega-3 versus 12.3 on placebo (HR 1.13, 95% CI 1.01 to 1.26, P=.03) — a small but statistically significant increase in risk. Mood scores did not differ (mean PHQ-8 change difference 0.03 points, 95% CI -0.01 to 0.07). The authors concluded the findings do not support using omega-3 supplements to prevent depression in adults.
Worth asking
The largest trial ever run found fish oil did not prevent depression and if anything nudged the risk slightly up — am I taking it for prevention, and if so is there any reason to keep going?
Source
Effect of Long-term Supplementation With Marine Omega-3 Fatty Acids vs Placebo on Risk of Depression or Clinically Relevant Depressive Symptoms and on Change in Mood Scores: A Randomized Clinical Trial. — Okereke OI, Vyas CM, Mischoulon D, Chang G, Cook NR, et al. (2021)
Top-tier peer-reviewed journal
Read the source: https://doi.org/10.1001/jama.2021.21187
DOI: 10.1001/jama.2021.21187
How this was scored
- Study design
- Randomised controlled trial
- Funding
- Mixed public and industry funding
- Published in
- Top-tier peer-reviewed journal
- Sample size
- 18,353
- Preregistered
- Yes
- Conflicts disclosed
- Yes
- Independent of proponent
- Yes
- Retracted
- No
Read the full scoring rubric, including what it can't tell you.
Published August 19, 2026.
Where we put this study in context
Questions
How strong is the evidence behind this?
Resolv rates this source "gold standard". Top of the evidence hierarchy, independently funded. It scores 85 out of 100 on our published rubric. One caveat travels with that badge: The higher depression rate was a borderline result on one of two coprimary outcomes while the other (mood scores) showed nothing at all; the authors did not claim omega-3 causes depression, and this was a prevention trial in people without clinically relevant depressive symptoms at baseline, so it does not test omega-3 as a treatment for existing depression. Study capsules and matching placebo were donated by Pronova BioPharma, an industry in-kind contribution, though the trial itself was NIH-funded, the funders had no role, and the result was unfavourable to the product. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
Effect of Long-term Supplementation With Marine Omega-3 Fatty Acids vs Placebo on Risk of Depression or Clinically Relevant Depressive Symptoms and on Change in Mood Scores: A Randomized Clinical Trial. — Okereke OI, Vyas CM, Mischoulon D, Chang G, Cook NR, et al. (2021). Published in: Top-tier peer-reviewed journal. DOI: 10.1001/jama.2021.21187. The full source is linked on this page so you can read it yourself.
Who paid for this research, and does that matter?
Study design: Randomised controlled trial. Funding: Mixed public and industry funding. The researchers were independent of whoever benefits from the result. Industry sponsorship is one of the most reliably measured biases in medicine, which is why funding carries real weight in the score rather than sitting in a footnote.
Is omega-3, fish oil, epa, dha, n-3 pufa, omega-3 fatty acids, krill oil, algal oil FDA approved for this use?
No. Its current status is: Not FDA-evaluated for this use. Fish-oil, EPA and DHA products sold for mood are dietary supplements under DSHEA: no FDA review of safety or effectiveness happens before they go on sale, and none is approved to treat depression or any other psychiatric condition. Prescription omega-3 drugs do exist, but for lipids, not mood.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.