Global hippocampal atrophy in major depressive disorder: a meta-analysis of magnetic resonance imaging studies

Abstract Introduction: Major depressive disorder (MDD), an incapacitating mental disorder, is characterized by episodes of at least 2 weeks of apparent changes in mood, cognition, and neurovegetative functions. Many neuroimaging studies using magnetic resonance imaging (MRI) have examined morphometric changes in patients with MDD, but the results are not conclusive. This study aims to review the literature and perform a meta-analysis on hippocampal volume (HcV) in patients with MDD. Methods: Studies on HcV in patients with MDD diagnosis were identified from major databases (MEDLINE, EMBASE, The Cochrane Library, Scopus, PsycINFO, and SciELO) using the search terms depression, major depressive disorder, MDD, unipolar, magnetic resonance imaging, MRI, and hippocampus. Results: A meta-analysis of 29 studies fulfilling specific criteria was performed. The sample included 1327 patients and 1004 healthy participants. The studies were highly heterogeneous with respect to age, sex, age of onset, and average illness duration. However, the pooled effect size of depression was significant in both hippocampi. MDD was associated with right (-0.43; 95% confidence interval [95%CI] −0.66 to −0.21) and left (-0.40; 95%CI −0.66 to −0.15) hippocampal atrophy. Conclusions: MDD seems to be associated with global HcV atrophy. Larger longitudinal follow-up studies designed to analyze the influence of sociodemographic variables on this relationship are required to yield better evidence about this topic.

摘要：重度抑郁症（Major Depressive Disorder, MDD）是一种致残性精神障碍，以持续至少2周的情绪、认知及神经自主功能显著改变为特征。既往诸多采用磁共振成像（Magnetic Resonance Imaging, MRI）的神经影像学研究均探讨了MDD患者的脑形态计量学改变，但相关研究结果尚未达成共识。本研究旨在针对MDD患者的海马体积（Hippocampal Volume, HcV）开展文献综述与荟萃分析。

方法：通过MEDLINE、EMBASE、The Cochrane Library、Scopus、PsycINFO及SciELO等主要数据库，以抑郁症、重度抑郁症、MDD、单相抑郁、磁共振成像、MRI及海马作为检索词，检索符合MDD诊断标准且探讨海马体积的相关研究。

结果：本研究对29项符合特定纳入标准的研究进行了荟萃分析，纳入样本共包含1327例MDD患者与1004名健康对照者。上述研究在年龄、性别、发病年龄及平均病程等维度均存在显著异质性。但双侧海马的合并效应量均具有统计学显著性：MDD与右侧海马萎缩（-0.43；95%置信区间[95%CI]：-0.66~-0.21）及左侧海马萎缩（-0.40；95%置信区间[95%CI]：-0.66~-0.15）显著相关。

结论：MDD似乎与全域海马体积萎缩存在关联。未来需开展更大样本量的纵向随访研究，分析社会人口学变量对这一关联的影响，以获取该领域更确凿的循证证据。