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A randomised controlled trial of dietary improvement for adults with major depression (SMILES)
12-week parallel RCT (n=67 analysed) of dietitian-delivered dietary improvement vs a social support control in adults with major depression: the diet arm showed greater Montgomery–Åsberg Depression Rating Scale improvement (Cohen's d = −1.16) and higher remission rates (32.3% vs 8.0%; NNT≈4.1).
Design
- SMILES: 12 weeks, parallel-group, single-blind
- Intervention: 7 dietitian sessions, modified Mediterranean dietary targets
- Control: matched social support visits (same schedule/length)
- Primary outcome: MADRS at 12 weeks (MMRM)
Results (per abstract)
- MADRS change: diet > control, t(60.7) = 4.38, P < 0.001, Cohen’s d = −1.16
- Remission (MADRS <10): 32.3% (10/31 completers) vs 8.0% (2/25); χ² P = 0.028; NNT ≈ 4.1 (95% CI 2.3–27.8)
- Adjunctive care: most participants were already using psychotherapy and/or pharmacotherapy
Evidence hygiene
Read linked BMC Med commentaries on expectation bias / recruitment—effect size is unusually large for nutritional psychiatry; treat as hypothesis-generating until replicated at scale.
Publication
Jacka FN, O'Neil A, Opie R, et al. BMC Med. 2017 Jan 30;15(1):23. PMID 28137247; ACTRN12612000251820.
Outcomes
- Effect Size (Cohen's d / SMD)-1.16d (Cohen's d)
- Remission (MADRS <10): 32.3% (10/31) diet support vs 8.0% (2/25) control among completers with 12-week data; NNT≈4.1 (95% CI 2.3–27.8).