Current state of nutritional psychiatry: A scoping review of randomized controlled trials

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.

Keywords: Nutritional psychiatry; Randomized controlled trial; Mendelian randomization; Fundamental research; Probiotics; Gut microbiota

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.