When most people are sad, they know the feeling is only temporary. But there are large numbers of people who stay sad for a long time. These people suffer from the common mental sickness known as depression.
Depression can affect anyone. Researchers say one out of ten persons in the world has the chance of developing a major depression at some time.
当大多数人在感到难过时，他们知道这种感觉只是暂时的。但是也有很多人的悲伤情绪会持续很长时间。这些人患有常见的精神疾病，即抑郁症。
每个人都有可能得抑郁症。研究人员表示，世界上有十分之一的人可能患上严重抑郁症。