We think we know. Yes, we suppose that people commit suicide when they are clinically depressed. The truth: actually, statistics show that most people who committed suicide did it when they were improving from their major depression.
You see, when someone is depressed for a significantly long time, they can get accustomed to the feelings and thus become unable to distinguish between happiness and misery. "I think I'm happy, but I'm not so sure" is a common thought made by these people. Now, most people do have that thought. We aren't really sure if we are happy, but we do think we're okay, unless something exiting happens. The difference is the behavior. A depressed person may be unable to tell that they are depressed, but his/her behavior may give other people a chance to really see what is going on inside. That is the difference.
When refered to a psychologist by a close person, the new client will undergo therapy. Since depression is a curable illness, there will be positive results. However, during the process, some people who didn't know previously that they were so depressed, will begin to actually feel what they were going through because of their ability to now compare their improving state and their past state. Fear results from that. Why? Some may think that they should have stayed depressed because if they did, they wouldn't have known this pain. And if depression is this painful and it can occur over and over again, improvement is a sign that this will come again in an endless absurd cycle. The wrist is slit, the neck is hung, the trigger is pulled, the overdose is taken, and the top of the skyscraper flies upward.

Responce to reviews:
eeerm: Thank you!

Courtney1991: Yes, it is a terrible thing. But, when you're about to commit suicide, everyone around you looks like someone who is going to hurt you badly and you begin to doubt that they will actually help you and that they will cause more pain to you in the future. You start to view all other people as harmful to your own existence.