A rated improvement in depressive symptoms in a population of schizophrenics could be attributable to (1) improvement in the underlying psychosis that secondarily affect depression measures (e.g. a subject's depression rating improves because he is happy because his hallucinations are less), (2) improvement in some psychotic symptoms may directly lower depression rating scores (e.g. improvement in negative symptoms of schizophrenia would lead to an improvement in depression ratings).