SYP and major depressive disorder: Disruption of synaptic plasticity is regarded as be one of the neurobiological mechanisms underlying depression.[31] The expression levels of synaptophysin (SYP) and postsynaptic densitin‐95 (PSD‐95), synaptic‐associated proteins in the hippocampus, serve as markers for evaluating synaptic integrity and plasticity.[32, 33] Previous researches have consistently demonstrated a significant reduction in their expression levels among patients with MDD,[34, 35] thus justifying their inclusion in this study.