PREDIMED: the Mediterranean diet arm had a hazard ratio of 0.78 for depression, and it was not significant
In the Spanish cardiovascular trial, 224 new cases of depression over at least three years. Mediterranean diet with nuts against low-fat control: HR 0.78 (95% CI 0.55 to 1.10), "not significant". Only the diabetes subgroup reached 0.59.
Reasonable evidence with real limitations. how we score evidence
Caveat on this rating: Primary result not significant (HR 0.78, 0.55 to 1.10); the quoted 0.59 is a diabetes subgroup. Older adults at high cardiovascular risk; depression was a secondary outcome. The olive oil arm is not reported in the abstract.
A large randomised trial with depression as an outcome, and its primary result missed. The subgroup that did not miss is the number that gets quoted.
Significant findings
PREDIMED was "a multicenter, randomized, primary prevention field trial of cardiovascular disease" in "community-dwelling men aged 55 to 80 years and women aged 60 to 80 years at high risk of cardiovascular disease (51% of them had type 2 diabetes; DM2) attending primary care centers affiliated with 11 Spanish teaching hospitals." The question here was "the effects of two Mediterranean diets versus a low-fat diet on depression risk after at least 3 years of intervention." Primary analyses were intention-to-treat.
"We identified 224 new cases of depression during follow-up. There was an inverse association with depression for participants assigned to a Mediterranean diet supplemented with nuts (multivariate hazard ratio (HR) 0.78; 95% confidence interval (CI) 0.55 to 1.10) compared with participants assigned to the control group, although this was not significant."
"However, when the analysis was restricted to participants with DM2, the magnitude of the effect of the intervention with the Mediterranean diet supplemented with nuts did reach statistical significance (multivariate HR = 0.59; 95% CI 0.36 to 0.98)."
The authors' conclusion: the diet with nuts "could exert a beneficial effect on the risk of depression in patients with DM2."
The other direction
The point estimate leaned the right way, 0.78, and a confidence interval that crosses one in a secondary outcome of a heart trial is not proof of no effect; it is a trial not built to answer this question. Older adults at high cardiovascular risk are not the general population and not people with depression. A subgroup result at 0.59 with an upper bound of 0.98 is the kind of finding that needs its own trial before it is believed. The other Mediterranean arm, with olive oil, is not reported in the abstract at all.
What this does not show
It does not test diet as a treatment for existing depression. It does not compare diet with any treatment. It does not tell anyone to eat nuts, and this row does not either.
Worth asking
When the main result misses and the subgroup hits, which number ends up in the headline?
Source
Mediterranean dietary pattern and depression: the PREDIMED randomized trial — Sánchez-Villegas A, Martínez-González MA, Estruch R, Salas-Salvadó J, Corella D, Covas MI, Arós F, Romaguera D, Gómez-Gracia E, Lapetra J, Pintó X, Martínez JA, Lamuela-Raventós RM, Ros E, Gea A, Wärnberg J, Serra-Majem L (2013)
Reputable peer-reviewed journal
Read the source: https://doi.org/10.1186/1741-7015-11-208
DOI: 10.1186/1741-7015-11-208
How this was scored
- Study design
- Randomised controlled trial
- Funding
- Funding not disclosed
- Published in
- Reputable peer-reviewed journal
- Sample size
- not recorded
- 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 "moderate evidence". Reasonable evidence with real limitations. It scores 64 out of 100 on our published rubric. One caveat travels with that badge: Primary result not significant (HR 0.78, 0.55 to 1.10); the quoted 0.59 is a diabetes subgroup. Older adults at high cardiovascular risk; depression was a secondary outcome. The olive oil arm is not reported in the abstract. 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?
Mediterranean dietary pattern and depression: the PREDIMED randomized trial — Sánchez-Villegas A, Martínez-González MA, Estruch R, Salas-Salvadó J, Corella D, Covas MI, Arós F, Romaguera D, Gómez-Gracia E, Lapetra J, Pintó X, Martínez JA, Lamuela-Raventós RM, Ros E, Gea A, Wärnberg J, Serra-Majem L (2013). Published in: Reputable peer-reviewed journal. DOI: 10.1186/1741-7015-11-208. 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: 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.