There is psychosis, in which a person is not in touch with reality, whose inner world is more real than the outer world we all live in. There are neurotics, people who are not able to manage their lives as they would like to. They find themselves doing things they don't want to do, compulsions. They are unable to do things they want to do, inner roadblocks they want to remove. They are depressed.
Depression affects at least all of the people some of the time.
It may have an organic cause, and it may have a spiritual cause, or both. I define depression as feeling low, perhaps debilitated, even when life is going well. Sometimes there is an organic cure. Very often there is a spiritual cure. An altered state of consciousness, experiences that can't be explained.