Very few people guess, but many, so to say, normal people can have such mental disease as depressive psychosis. Its main difference is often changing mood. At the same time there can be so sharp differences that under the influence of psychosis of people can commit not only offense, but also a suicide.
The depression is one of the most frequent reasons of the address to psychologists and psychotherapists. And rather often not sufferers, but their relatives or friends wishing to help address. "The husband has a depression what to do?", "How to help the girlfriend to get rid of a depression?", "The wife has after the child's birth a depression what to make to help it?", "To become intolerable an autumn depression what to do?" - a set of similar questions not a rarity for experts in psychology.