Researchers assessed how often people drink tea, in what quantities, and which specific varieties they choose. The most noticeable link to a reduced likelihood of depressive states was found among those who prefer semi-fermented and unfermented types of the beverage, particularly oolong and green tea. This effect was more frequently observed in individuals who limited themselves to one or two cups a day. The researchers also noted that a lower prevalence of depression was more often found among those who drink tea daily. No such dependence was identified with infrequent consumption, but a large quantity of the beverage (three or more cups per day) did not show any significant additional effect. According to the authors of the study, the possible influence may be attributed to the bioactive components found in tea — polyphenols and the amino acid theanine. They are known for their antioxidant and anti-inflammatory properties and can affect the brain's neurotransmitters.