Functional outcome and service engagement in major depressive disorder with psychotic features: comparisons with schizophrenia, schizoaffective disorder and bipolar disorder in a 6-year follow-up of the Cavan-Monaghan First Episode Psychosis Study (CAMFEPS).

At 6-year follow-up, these diagnoses are characterized by quantitative rather than qualitative differences in psychopathology, functionality, quality of life, and service engagement, with considerable overlap between them. These findings suggest that MDDP should join SZ, SA, and BD in a milieu of psychosis that transcends arbitrary boundaries.