As if all those studies on physical health and green tea were not enough, a new wave of scientific studies are being published that discuss the relationship between green tea consumption and mood.

The latest of these is a study from Japan that found an association between green tea consumption and depression in elderly men and women (the study defined “elderly” as anyone aged at least 70 years). The researchers found that a high consumption of green tea was related significantly to lower rates of symptoms of depression.

Why this works, though, remains unanswered. Here is one theory:

Green tea has an anti-stress mechanism that might help explain the results. Theanine, a component of green tea, has been shown in animal studies to increase brain serotonin and dopamine concentrations. These are the “feel good” hormones.

In any case, this study corroborates previous studies, which also showed a decrease in psychological distress in Japanese people, who drank significant amounts of green tea.

Niu K et al. 2009. Green tea consumption is associated with depressive symptoms in the elderly. Am J Clin Nutr. 2009 Dec;90(6):1615-22.