Tea and Its Active Ingredients in Preventing and Alleviating Depression: A Comprehensive Review.

Depression, commonly known as unipolar affective disorder, is one of the most prevalent mental illnesses in contemporary society, affecting individuals to varying degrees. Tea is one of the three major non-alcoholic beverages globally; it has a rich history of consumption and is associated with numerous health and nutritional benefits. This review systematically summarizes the antidepressant effects of various bioactive compounds found in tea, drawing upon research findings in the field of tea's functional health. It elucidates the impact of tea's bioactive components on the hypothalamic-pituitary-adrenal (HPA) axis, the nervous system, the immune system, intestinal microflora, and the monoaminergic system, among other physiological sites, to achieve antidepressant effects. These effects primarily involve enhancing neural signaling pathways, regulating neural signaling molecule levels, and reducing neuroinflammation. Tea may normalize the body's nervous system by bolstering immune function, alleviating or eliminating cellular inflammation to maintain healthy homeostasis, or improving intestinal flora and mitigating stress to prevent or treat depressive disorders. Additionally, the potential social support derived from tea-drinking activities, such as cultural rituals and interpersonal communication, may contribute to its antidepressant effects. This review discusses and analyzes the current research status regarding the antidepressant effects of tea and highlights that tea and its active ingredients can be utilized to prevent and alleviate depression.