# Plant-based diets and depression: epidemiological evidence, biological mechanisms, and implications for prevention

## TL;DR

Eating more healthy plant-based foods may lower depression risk by improving inflammation, gut health, and nutrient intake.

## Contribution

This paper reviews how the quality of plant-based diets, not just their composition, affects depression risk and mental health.

## Key findings

- Healthful plant-based diets correlate with reduced depressive symptoms and better mental health.
- Unhealthy plant-based diets high in ultra-processed foods increase depression risk.
- Diet quality and nutrient intake are more important than simply avoiding animal foods.

## Abstract

Depression is a leading global mental health burden, and diet has emerged as a modifiable risk factor. This narrative review summarizes evidence about the association between plant-based dietary patterns and depression. It focuses particularly on diet quality and potential mechanisms. We examined plant-based diets—defined by the Plant-Based Diet Index (PDI), healthy PDI (hPDI), and unhealthy PDI (uPDI)—and plant-forward dietary patterns such as the Mediterranean, DASH, and MIND diets in relation to depressive symptoms or diagnosed depression. In diverse populations, greater adherence to healthful plant-based dietary patterns that emphasize minimally processed plant foods typically correlates with reduced depressive symptoms, better mental health, and improved quality of life. Conversely, diets that are high in ultra-processed, energy-dense plant foods are associated with a higher risk of depression. Proposed mechanisms include reduced systemic inflammation, beneficial modulation of the gut microbiota and the microbiota–gut–brain axis, and improved intake of key nutrients and phytochemicals involved in monoamine neurotransmission, neurotrophic signaling, and oxidative stress defense. In general, the influence of plant-based diets on depression seems to be more closely related to diet quality and nutrient adequacy rather than merely the elimination of animal foods.