Nagamine T. Current state of nutritional psychiatry: A scoping review of randomized controlled trials. World J Methodol 2025; 15(4): 104664 [DOI: 10.5662/wjm.v15.i4.104664]
Corresponding Author of This Article
Takahiko Nagamine, MD, PhD, Department of Psychiatric Internal Medicine, Sunlight Brain Research Center, 4-13-18 Jiyugaoka, Hofu 7470066, Yamaguchi, Japan. anagamine@yahoo.co.jp
Research Domain of This Article
Psychiatry
Article-Type of This Article
Systematic Reviews
Open-Access Policy of This Article
This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
World J Methodol. Dec 20, 2025; 15(4): 104664 Published online Dec 20, 2025. doi: 10.5662/wjm.v15.i4.104664
Current state of nutritional psychiatry: A scoping review of randomized controlled trials
Takahiko Nagamine
Takahiko Nagamine, Department of Psychiatric Internal Medicine, Sunlight Brain Research Center, Hofu 7470066, Yamaguchi, Japan
Author contributions: Nagamine T designed and conceived the study, collected the data, analyzed and interpreted the results, drafted the manuscript, and has read and agreed to the published version of the manuscript.
Conflict-of-interest statement: The authors have no conflicts of interest to declare.
PRISMA 2009 Checklist statement: The authors have read the PRISMA 2009 Checklist, and the manuscript was prepared and revised according to the PRISMA 2009 Checklist.
Open Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Takahiko Nagamine, MD, PhD, Department of Psychiatric Internal Medicine, Sunlight Brain Research Center, 4-13-18 Jiyugaoka, Hofu 7470066, Yamaguchi, Japan. anagamine@yahoo.co.jp
Received: December 28, 2024 Revised: February 25, 2025 Accepted: March 4, 2025 Published online: December 20, 2025 Processing time: 220 Days and 11.7 Hours
Abstract
BACKGROUND
Nutritional psychiatry is a rapidly expanding field of research, with mounting evidence suggesting that nutritional factors may play a role in the development of psychiatric disorders.
AIM
To examine the level of evidence for nutritional psychiatry.
METHODS
A scoping review was conducted to assess the current state of nutritional psychiatry, including a search for randomized controlled trials (RCTs).
RESULTS
The review identified a total of seven papers, with many concentrating on the relationship between depression and the gut microbiome. A salient issue that emerged from this review was the paucity of sample size in many studies. The inherent complexity of nutritional studies, characterized by a multitude of potential factors and exposures that often act as confounders, poses significant challenges to the development of effective RCT designs. The analysis revealed that probiotics, though demonstrating efficacy, exhibited a modest effect size.
CONCLUSION
Conducting RCTs with effective markers is imperative from these studies. The implementation of Mendelian randomization and the investigation of mechanisms in basic research are essential complementary approaches.
Core Tip: The number and quality of randomized controlled trials (RCTs) in the field of nutritional psychiatry remain inadequate. The relationship between nutrition and psychiatric disorders is challenging to demonstrate causally in RCTs due to the multitude of confounding factors and the relatively modest effect sizes observed. To enhance the evidence base in nutritional psychiatry, it would be beneficial to utilize not only RCTs but also data from Mendelian randomization studies and fundamental research, with the aim of elucidating the underlying mechanisms.
