Frequent consumption of green tea is associated with a lower prevalence of depression in the elderly. Green tea intake was determined in a cohort of 1058 elderly Japanese subjects (70+ years old). In this cohort, 34.1% had mild depressive symptoms and 20.2% had severe depressive symptoms.

The results showed that, compared with those who consumed one or less cup of green tea per day, those who drank four or more cups per day were 44% less likely to have symptoms of depression. (Green tea consumption is associated with depressive symptoms in the elderly. Am J Clin Nutr. 2009 Dec;90(6):1615-22).