Systematic Reviews
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Psychiatr. Aug 19, 2020; 10(8): 187-201
Published online Aug 19, 2020. doi: 10.5498/wjp.v10.i8.187
Dietary modification in the treatment of schizophrenia spectrum disorders: A systematic review
Monique Aucoin, Laura LaChance, Sam N Clouthier, Kieran Cooley
Monique Aucoin, Sam N Clouthier, Kieran Cooley, Department of Research and Clinical Epidemiology, Canadian College of Naturopathic Medicine, Toronto M2K 1E2, Canada
Laura LaChance, Department of Psychiatry, McGill University, Montreal H3A 0G4, Canada
Laura LaChance, Centre for Addiction and Mental Health, Toronto M6R 1A1, Canada
Kieran Cooley, Department of Public Health, Australian Research Centre in Complementary and Integrative Medicine, University of Technology Sydney, Ultimo 2007, Australia
Kieran Cooley, Department of Doctoral Acupuncture and Chinese Medicine, Pacific College of Health Science, San Diego, CA 92108, United States
Author contributions: Aucoin M and LaChance L conceived of this project, completed article screening, data extraction, analysis and interpretation as well as manuscript preparation; Clouthier SN completed additional data extraction and preparation of components of the manuscript; Cooley K contributed to data analysis and interpretation as well as components of the manuscript preparation; all authors read and approved the final manuscript.
Conflict-of-interest statement: The authors report no conflict of interest.
PRISMA 2009 Checklist statement: The authors confirm that the manuscript was prepared 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:
Corresponding author: Monique Aucoin, Research Fellow, Department of Research and Clinical Epidemiology, Canadian College of Naturopathic Medicine, 1255 Sheppard Ave E, Toronto M2K 1E2, Canada.
Received: March 20, 2020
Peer-review started: March 20, 2020
First decision: April 26, 2020
Revised: June 25, 2020
Accepted: July 19, 2020
Article in press: July 19, 2020
Published online: August 19, 2020
Research background

Schizophrenia spectrum disorders (SSD) impact functioning, reduce quality of life and increase the risk of physical illness and premature mortality. Several observational and preclinical studies suggest a role of diet in the development and progression of SSD and rigorous clinical trials designed to assess the impact of adjunctive diet interventions in patients with major depression have reported benefit.

Research motivation

Nutritional intervention studies aimed at decreasing body weight have demonstrated efficacy in improving metabolic outcomes; however, few studies have explored the impact of interventions designed to modify diet on mental health outcomes. Systematic review of this body of literature has not been previously conducted.

Research objective

This systematic review sought to synthesize the existing experimental studies of adjunctive diet modification as an intervention in the treatment of psychotic disorders, analyze findings related to effectiveness and safety, highlight knowledge gaps and limitations, and set forward recommendations for future research studies.

Research methods

An extensive a priori search strategy was developed and the databases Embase, Embase Classic, Ovid MEDLINE were searched. Screening and data extraction were completed in duplicate. Studies included in this analysis were experimental studies of an adjunctive dietary intervention (overall dietary pattern or education on dietary change) for treatment of SSD. No restrictions were placed on control groups or blinding. The studies were required to report a mental health outcome.

Research results

Twenty-five clinical trials were identified, along with two additional protocols and two meta-analyses. Of the 25 clinical trials, four employed both blinding and randomization. Five studies used a control group and randomization but no blinding while another six studies used a control group but lacked randomization and blinding. The remaining ten trials were completed with no control group. The average sample size was 171 participants and the average duration was 33 wk. The interventions consisted primarily of nutritional education; however, the nutrition advice provided to participants was poorly described overall and compliance was not assessed. All of the studies included lifestyle or psychosocial components in addition to dietary modification. Of the 27 protocols, twelve were designed with mental health symptoms as the primary outcome. A high level of heterogeneity was found with respect to patient population, intervention, and study design. Nineteen of the clinical trials reported improvement in one or more mental health domain including psychosis symptoms, cognition, and quality of life. The studies that showed benefit tended to have a smaller sample size and were less likely to be randomized but were more likely to use a group delivery intervention. Adverse events were not generally reported.

Research conclusions

The findings of this systematic review suggest that adjunctive diet interventions may be useful in the management of mental health symptoms in SSD; however, limitations in the existing research preclude clear conclusions.

Research perspectives

Further research assessing effectiveness and efficacy of clearly reported dietary interventions is warranted, especially those identifying mental health symptoms as their primary outcome, using rigorous methodology (control group and blinding), modifying diet in isolation from other health behaviours and assessing participant compliance.