Oh, and it's a shame that viewers as well as critics disagree with your opinion of the film. Based on your reasoning, may I suggest that you may be suffering from some sort of social ineptness?

Cool, except he's not depressed, his friends are not depressed, and even the new friend he meets is not depressed.
Could it be that you're depressed and can only see it in others?
Just so you know, when people feel disconnected, it doesn't mean depressed. When we're confused, it doesn't mean depressed. You can have several decomposating mental issues from delusions to religious issues and not be depressed.
My guess, if the mother ended her life, then she was probably suffering from depression.