The certainty of the evidence on plant vs meat predominant dietary patterns and depression: An umbrella review

Context:
Diets rich in plant foods are associated with reduced risk of depressive symptoms. However, studies report greater depressive symptomology in those who follow a plant-predominant dietary pattern. Meta-analyses and systematic reviews of plant and meat-predominant diets and depression highlight conflicting results.

Objectives:
This umbrella review applied A Measurement Tool to Assess Systematic Reviews (AMSTAR2) to explore the state of evidence on plant and meat-predominant dietary patterns and depression.

Data Sources:
Six databases were searched from inception to Jan 2025 CINAHL, MEDLINE, PsycINFO, Psychology and Behavioural Sciences Collection, Scopus and Web of Science.

Data Extraction:
Data were extracted by two independent researchers using Covidence software.

Data Analysis:
The search revealed 104 studies, nine met inclusion criteria. Data were synthesised narratively grouped by plant-predominant dietary patterns and meat-predominant dietary patterns.

Conclusions:
Five papers reported associations between plant and meat-predominant dietary patterns and depression, four reported plant-predominant dietary patterns increased depression, and five found conflicting or no associations. Similar systematic search terms, overlap of primary studies and short timeframes between reviews raises concerns about the validity and scientific contribution of repeated systematic review on this topic. We highlight the need for greater awareness of methodological issues, including high reliance on observational studies, high levels of heterogeneity, imprecision of measurement tools, and lack of measurement of dietary adherence and composition.