Pooled across 16 trials and 45,826 people, diet moved depression by a small g of 0.16 and anxiety not at all
The meta-analysis of randomised trials: "dietary interventions significantly reduced depressive symptoms (g = 0.162, 95% CI = 0.055 to 0.269)". Fifteen of sixteen trials were in people without clinical depression. Anxiety: no effect.
Well-supported by good-quality research. how we score evidence
Caveat on this rating: Fifteen of sixteen trials were in nonclinical samples, so the pooled effect is mostly about mood in the general population. g 0.16 is small. Two errata were published and were not read for this row.
This is what the diet evidence looks like once every randomised trial is counted, not just the three small ones with big effects.
Significant findings
"Sixteen eligible randomized controlled trials (published in English) with outcome data for 45,826 participants were included; the majority of which examined samples with nonclinical depression (n = 15 studies)."
"Nonetheless, dietary interventions significantly reduced depressive symptoms (g = 0.162, 95% CI = 0.055 to 0.269, p = 0.003)."
The effect held in the better trials and against both kinds of control: "Similar effects were observed among high-quality trials (g = 0.171, 95% C.I.=0.057 to 0.286, p=0.003) and when compared with both inactive (g = 0.114, 95% C.I.=0.008 to 0.219, p=0.035) and active controls (g = 0.224, 95% C.I.= 0.052 to 0.397, p = 0.011)."
For anxiety, nothing: "No effect of dietary interventions was observed for anxiety (k = 11, n = 2270, g = 0.085, 95% C.I. = -0.031 to 0.202, p=0.151)."
One subgroup stood out: "Studies with female samples observed significantly greater benefits from dietary interventions, for symptoms of both depression and anxiety."
The authors: "Dietary interventions hold promise as a novel intervention for reducing symptoms of depression across the population."
The other direction
A g of 0.16 is small. It is the size of effect that is real and that most people would not notice in themselves. Fifteen of the sixteen trials were in people without clinical depression, so the pooled number is mostly about mood in the general population, not about treating a disorder; the one trial in clinical depression is the SMILES row. The trials were heterogeneous in what "dietary intervention" meant. And the case for diet is also here: the effect survived restriction to high-quality trials and to active controls, which is where weak effects usually vanish.
What this does not show
It does not compare diet with medication or therapy. It does not show that diet treats major depression; one trial in the set tested that. It does not tell anyone to change what they eat, and this row does not either.
Worth asking
If the effect is small and mostly in people who were not depressed, what is the claim that it treats depression actually resting on?
Source
The Effects of Dietary Improvement on Symptoms of Depression and Anxiety: A Meta-Analysis of Randomized Controlled Trials — Firth J, Marx W, Dash S, Carney R, Teasdale SB, Solmi M, Stubbs B, Schuch FB, Carvalho AF, Jacka F, Sarris J (2019)
Reputable peer-reviewed journal
Read the source: https://doi.org/10.1097/PSY.0000000000000673
DOI: 10.1097/PSY.0000000000000673
How this was scored
- Study design
- Meta-analysis of randomised trials
- Funding
- Funding not disclosed
- Published in
- Reputable peer-reviewed journal
- Sample size
- 45,826
- Preregistered
- Yes
- Conflicts disclosed
- not recorded
- Independent of proponent
- not recorded
- Retracted
- No
Read the full scoring rubric, including what it can't tell you.
Published September 29, 2026.
Questions
How strong is the evidence behind this?
veisund rates this source "strong evidence". Well-supported by good-quality research. It scores 76 out of 100 on our published rubric. One caveat travels with that badge: Fifteen of sixteen trials were in nonclinical samples, so the pooled effect is mostly about mood in the general population. g 0.16 is small. Two errata were published and were not read for this row. 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?
The Effects of Dietary Improvement on Symptoms of Depression and Anxiety: A Meta-Analysis of Randomized Controlled Trials — Firth J, Marx W, Dash S, Carney R, Teasdale SB, Solmi M, Stubbs B, Schuch FB, Carvalho AF, Jacka F, Sarris J (2019). Published in: Reputable peer-reviewed journal. DOI: 10.1097/PSY.0000000000000673. 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: Meta-analysis of randomised trials. Funding: Funding not disclosed. Independence from the proponent is not recorded. 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 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.