Growing evidence indicates the community of microorganisms throughout the gastrointestinal tract, (i.e., gut microbiota), is associated with anxiety and depressive disorders. We present the first systematic review of the gut microbiota in anxiety disorders, along with an update in depression. Consideration of shared underlying features is essential due to the high rates of comorbidity. Systematic searches, following PRISMA guidelines, identified 26 studies (two case-control comparisons of the gut microbiota in generalised anxiety disorder, 17 in depression, one incorporating both anxiety/depression, and five including symptom-only measures). Alpha and beta diversity findings were inconsistent; however, differences in bacterial taxa indicated disorders may be characterised by a higher abundance of proinflammatory species (e.g., Enterobacteriaceae and Desulfovibrio), and lower short-chain fatty acid producing-bacteria (e.g., Faecalibacterium). Several taxa, and their mechanisms of action, may relate to anxiety and depression pathophysiology via communication of peripheral inflammation to the brain. Although the gut microbiota remains a promising target for prevention and therapy, future research should assess confounders, particularly diet and psychotropic medications, and should examine microorganism function.

越来越多的证据表明整个胃肠道的微生物群落（即肠道微生物群）与焦虑和抑郁症有关。我们首次对焦虑症中的肠道微生物群进行系统评价，同时对抑郁症进行了更新。由于合并症的发生率很高，因此必须考虑共享的潜在特征。遵循 PRISMA 指南的系统搜索确定了 26 项研究（两项针对广泛性焦虑症的肠道微生物群的病例对照比较，17 项在抑郁症中的比较，一项包含焦虑/抑郁症，五项包含仅针对症状的措施）。Alpha 和 Beta 多样性结果不一致；然而，细菌分类群的差异表明疾病可能以更高丰度的促炎物种为特征（例如，肠杆菌科和脱硫弧菌），以及低级短链脂肪酸产生菌（如粪杆菌）。几种分类群及其作用机制可能通过将外周炎症传递到大脑而与焦虑和抑郁的病理生理学有关。尽管肠道微生物群仍然是预防和治疗的一个有希望的目标，但未来的研究应该评估混杂因素，特别是饮食和精神药物，并应该检查微生物的功能。