Nocapszy said it. The established field of psychology is a logical disaster zone. Everyone knows of someone with real mental illness. Schizophrenia is real, and obvious.
Not to lower peoples' problems to something not worth worrying about, but they usually aren't biological in origin. They're the result of today's commonly mundane existence. When you're fighting for your existence 12 hours a day, as were many of our ancestors, you don't have time to worry about your level of contentment or go into a loop of obsession on the negative.