BDNF and major depressive disorder: Studies have shown that Quercetin alleviates MDD induced by chronic unpredictable mild stress in mice by reducing IL-1β and TNF-α expression in the hippocampus, increasing 5-hydroxytryptamine and brain-derived neurotrophic factor expression, and inhibiting neuroinflammation and apoptosis.[24] Prolonged immobility time in the forced swimming and tail suspension tests indicates extended periods of despair and hopelessness, reflecting weakened willpower, increased negative emotions, and a lack of spontaneous and exploratory behavior in mice.