Genome-wide DNA methylation in an animal model and human studies of schizophrenia: a protocol for a meta-analysis.

Introduction and objective: Neuropsychiatric disorders like schizophrenia are heterogeneous in that they occur because of the interaction of factors. These factors include but are not limited to genetic, epigenetic, neurobiological and environmental factors. Methylation of DNA, like other erpigenetic modifications, is risk factors for neuropsychiatric disorders. Candidate gene approach projects have produced contradictory results to find candidate gene methylation. The current genome-wide studies have limitations.

Search strategy: An exhaustive search strategy was designed to recover studies on genome-wide DNA methylation in schizophrenia patients or schizophrenia rat models. The Medline (PubMed), SCOPUS and Web of Science, databases were searched, giving 4077 references in total.

Screening and annotation: Studies will undergo two phases of screening, title and abstract screening and article screening, for inclusion by two reviewers. A third reviewer will resolve any disagreements in the article screening phase. Data will be collected using the Systematic Review Facility (http://syrf.org.uk/) tool. All included studies will undergo study quality and risk of bias assessment.

Data management and reporting: Data will be extracted and used to calculate effect sizes. For the purpose of this meta-analysis, a random effects model will be used to combine effect sizes. Heterogeneity will be assessed, and the sources identified. A risk-of-bias assessment will be carried out to assess the quality of the studies. An assessment of publication bias will also be carried out.

Ethics and dissemination: No ethical approval is required as there are no participants in the study. We will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses reporting guidelines and disseminate the findings through publication and conference presentation.

Prospero registration number: CRD42021283159.