Elderly people who drink several cups of green tea a day are less likely to suffer from depression, probably due to a "feel good" chemical found in this type of tea, Japanese researchers said.

Several studies have linked drinking green tea to lessening psychological problems and Kaijun Niu, of Tohoku University Graduate School, and colleagues found people aged 70 and older who drank four or more cups of green tea daily were 44 percent less likely to experience depression.

Green tea is widely consumed in many Asian countries, including China and Japan.

Niu's team investigated 1,058 relatively healthy elderly men and women. About 34 percent of the men and 39 percent of the women had symptoms of depression, according to the study that was published in the the American Journal of Clinical Nutrition.

A total of 488 participants said they drank four or more cups of green tea a day, 284 said they downed two to three cups daily and the rest reported having one or fewer cups daily.

According to the researchers, the apparent effect of drinking more green tea on alleviating symptoms of depression did not fade after they factored in social and economic status, gender, diet, history of medical problems and use of antidepressants.

There was no association between consumption of black or oolong tea, or coffee, and lower symptoms of depression.

A green tea component, the amino acid theanine, which is thought to have a tranquillising effect on the brain, may explain the "potentially beneficial effect" shown in the current study, Niu noted, adding that more study is needed.

日本研究人员日前称，老年人每天喝几杯绿茶可降低患抑郁症的风险，这可能是因为绿茶中含有一种能让人"感觉良好"的化学物质。

之前的几项研究发现，喝绿茶有助于减少心理问题。日本东北大学研究生院的丹生介顺及其同事发现，每天喝四杯或四杯以上绿茶的70岁及以上的老年人患抑郁症的几率比那些不喝绿茶的人低44%.

在中国和日本等很多亚洲国家，绿茶是一种很流行的饮品。

丹生的研究小组对1058名相对较健康的老年男性和女性进行了调查，约34%的男性和39%的女性有抑郁症状。该研究在《美国临床营养期刊》上发表。

共有488名调查对象称他们每天喝四杯或四杯以上的绿茶，284人说他们每天喝两到三杯，其他人每天喝一杯或喝得很少。

研究人员称，多喝绿茶对于缓解抑郁症状有显着效果，而且即便将社会经济状况、性别、饮食、病史和服用抗抑郁药等因素都考虑进去，这种效果也不会受到影响。

不过饮用红茶、乌龙茶或咖啡对减轻抑郁症状没有什么效果。

丹生指出，绿茶中所含的茶氨酸成分对于大脑有镇定作用，这或许可以解释这项研究所发现的绿茶的"潜在益处",不过还需进一步研究加以论证。