Mood disorder with psychotic features, schizoaffective disorder, and schizophrenia with mood features: trouble at the borders.

Psychiatry has long struggled with the problem of how to understand the relationship between psychotic symptoms and mood symptoms. In the past, these debates were over conceptualizations of categories based on syndromal definitions of mental illnesses. Ample data now exists that provide insight into the biologic basis for syndromal distinctions. We examine the syndromes of mood disorder with psychotic features, schizoaffective disorder, and schizophrenia with mood features, reviewing their classification, clinical features, course, and treatment. We provide evidence that, clinically, mood disorders and schizophrenia do not separate neatly. We will also review data arising from studies in brain imaging, molecular neurobiology, and genetics. Evidence is accumulating that overlap across diagnostic boundaries for both pathologic and etiologic factors exist, along with disorder-specific factors. The nosology that will carve the reality of psychotic illness at the joints awaits further advances in genetics and neurobiology. Or, alternatively, carving out categories may turn out to be less useful for some purposes than considering dimensions.