From classical Chinese formula to modern mechanism: how Xiao-Yao-San modulates key signaling pathways in depression

Depression is a widespread mental disorder with profound effects on both physical and psychological health. Aberrant signal transduction contributes to depression by impairing neuronal function, reducing synaptic plasticity, and disrupting neurotransmitter transmission. Aberrant signal transduction can impair neuronal function, reduce synaptic plasticity, and disrupt neurotransmitter transmission, thereby contributing to the development of depression. Xiao-Yao-San (XYS), a traditional Chinese medicine (TCM) formula, has been extensively employed in the treatment of depression, with a broad therapeutic profile. This review aims to critically assess current scientific evidence on the antidepressant effects of XYS, focusing on its modulation of key signaling pathways. The goal is to provide a more robust mechanistic foundation for XYS-based therapies and offer insights for developing novel antidepressants that target signaling pathways. We systematically searched PubMed, Web of Science, ScienceDirect, CNKI, and Wanfang databases from inception to May 1, 2025, using relevant terms to identify studies on XYS and its active components, particularly those elucidating its regulation of signaling pathways involved in depression. XYS and its active ingredients modulate several crucial signaling pathways implicated in depression, including the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt), NOD-like receptor family pyrin domain containing 3 (NLRP3), nuclear factor-kappa B (NF-κB), and mitogen-activated protein kinase (MAPK) pathways. The antidepressant effects of XYS are primarily mediated through anti-inflammatory actions, improved hippocampal architecture, suppression of neuronal and mitochondrial apoptosis, reduction of oxidative stress, and enhancement of synaptic plasticity. Despite current limitations, this review identifies future research directions focusing on unexplored and cross-linked signalling pathways, which may support the development of signalling-targeted antidepressant agents based on XYS.