Schizophrenia: Disease, syndrome, or dimensions?

Schizophrenia has the status of a clinical syndrome and may comprise a number of specific disease entities. This construct is similar to dementia, in which several diseases have been defined within the syndrome. Alternatively, schizophrenia may be a single disease entity with quite variable manifestations across cases. Kraepelin proposed dementia praecox as a disease entity, and Bleuler proposed dissociative pathology as fundamental to each case, thus substantiating the single disease entity concept. More recently, the nuclear schizophrenia construct defined the disease entity using specific criteria proposed by Schneider and Langfeldt. This view has been challenged by a series of studies during the past three decades. These investigations are summarized in this report. Implications for clinical work with families are considered.