The Major Depressive Disorder (MDD), is a group of symptoms of mood disorders or affective disorders, with long-last depressive feelings as the central feature.

• 抑郁症是有各种原因引起的以抑郁为主要症状的一组心境障碍或情感性障碍，是一组以抑郁心境的自我体现为中心的临床症候群。