There are 4 axis on which a psychological profile is built.
Depression, Psychotic, Paranoia, & Schizophrenia are all on different axis.
So a paranoid schizophrenic is suffering from problems in 2 areas. Any of these can exist separately or in combination involving up to all 4.
One does not cause the other.
This is not a psychiatric/psychological definition; but just a quick explanation from a person to others people. In other words I am not a medical person & this is not meant for medical people.