It is a severe and prolonged state of mind in which normal sadness grows into a painful state of hopelessness, listlessness, lack of motivation, and fatigue. But, however well defined, clinical depression is many things to many people, varying from mild to severe.
一生中曾受过临床抑郁症影响的人口大约占人口总数的四分之一左右。这是一种长期而严重的精神疾病，得这种病的患者从正常的悲伤转化成一种失望、冷漠、委靡和疲惫的精神状态。但无论界定何等精确，临床抑郁症对不同的人都有着不同的含义，对患者的影响也从轻微到严重各不相同。