Comprehensive study on the impact of tea (Camellia sinensis) on human mental health

Tea, particularly the green, black, and oolong varieties derived from the Camellia sinensis plant, is widely consumed across the globe and has been associated with neuroprotective effects in human studies. This research synthesised findings from 318 studies sourced from PubMed, with an emphasis on 18 relevant studies, to evaluate the impact of tea, including its constituents L-theanine and epigallocatechin gallate (EGCG), on brain function and neurodegenerative conditions such as memory loss and cognitive decline. The results from both intervention and observational studies indicate that tea positively influences psychological well-being, cognitive abilities, and brain function, particularly in reducing anxiety, enhancing memory, and improving attention. The analysis, conducted using the restricted maximum likelihood model, confirmed a beneficial effect size of 0.50 for tea, with no evidence of publication bias, underscoring its significance in promoting nervous system activity.