 A study done over a two-year time period shadowing patients with schizophrenia and monitoring their depression was unable to locate possible triggers such as the ones previously listed, so it is possible the nature of schizophrenia itself is the primary cause of post-schizophrenic depression.Those suffering from post-schizophrenic depression are also commonly at risk for suicidal tendencies.There is a trend correlated between suicide and post-schizophrenic depression according to Mulholland and Cooper's research in "The Symptoms of Depression in Schizophrenia and its Management."