Search strategy for Pubmed databases.

Background
Depression post-myocardial infarction (MI) is becoming more prevalent. The gut-brain axis (GBA), influenced by the gut microbiota, is a critical component in understanding depression post-MI. Despite the well-established connection between gut microbiota and depression post-MI, this relationship remains incompletely understood.
Methods and analysis
This protocol will follow the Preferred Reporting Items for Systematic Review and Meta-analysis Protocol (PRISMA-P) 2020 statement. Beginning from inception to October 2023, a systematic search will be conducted across eight electronic databases, including PubMed, MEDLINE, Scopus, Embase, Cochrane Clinical Trials Database, Web of Science, China National Knowledge Infrastructure, and China Biomedical Literature Database. Pre-selected studies will be independently assessed by two researchers following a standard inclusion, data extraction and quality assessment protocol. The primary outcome measures are differences in the profile of gut microbiota and rating scale scores for depression. Fixed-effects models will be used when both clinical heterogeneity and statistical heterogeneity are low, otherwise random-effects models will be used. Furthermore, subgroup analyses will be conducted on the depression severity of the participants using the same psychiatric scales employed, study type and geographic region. Random forest plot runs and research-related statistical analyses will be carried out using Rev Man V.5.3 software.
Expected results
This study will identify the association between the gut microbiota and the onset of depression post-MI, and provide evidence for the use of probiotics as an adjunctive treatment for depression post-MI.
Trial registration
Prospero registration number:CRD42023444026.

背景
心肌梗死（myocardial infarction, MI）后抑郁症的发病率日益升高。受肠道菌群调控的肠-脑轴（gut-brain axis, GBA）是解析MI后抑郁症发病机制的关键环节。尽管已有研究证实肠道菌群与MI后抑郁症存在关联，但二者间的具体调控关系仍未完全阐明。

方法与分析
本研究方案将遵循《系统评价与Meta分析方案报告规范（Preferred Reporting Items for Systematic Review and Meta-analysis Protocol, PRISMA-P）2020版》。检索时限为建库至2023年10月，将在8个电子数据库中开展系统检索，包括PubMed、MEDLINE、Scopus、Embase、Cochrane临床对照试验数据库、Web of Science、中国知网（China National Knowledge Infrastructure, CNKI）及中国生物医学文献数据库。由2名研究者按照标准的纳入排除标准、数据提取及质量评价流程独立评估预筛选后的文献。主要结局指标为肠道菌群谱差异及抑郁症评定量表得分。若临床异质性与统计学异质性均较低，则采用固定效应模型合并分析；反之则采用随机效应模型。此外，将根据参与者的抑郁症严重程度（采用统一精神评定量表评估）、研究类型及地理区域进行亚组分析。本研究将使用Rev Man V.5.3软件完成森林图绘制及相关统计分析。

预期结果
本研究将明确肠道菌群与MI后抑郁症发病的关联，并为益生菌作为MI后抑郁症辅助治疗手段提供循证依据。

试验注册
Prospero注册编号：CRD42023444026。