New diagnostic issues in schizophrenic disorders.

The evolution of our understanding of schizophrenia has provided new concepts that substantially alter answers to questions such as age of onset, distribution by sex, and treatment response. Moreover, these new concepts offer heuristic advantages in etiopathophysiological study designs and permit investigators to address key sources of artifact. We discuss the unitary versus the clinical syndromal concept of schizophrenia and describe the implications of the latter with regard to the study of schizophrenia. We also present a heuristic tripartite division of schizophrenic symptoms for reducing syndromal heterogeneity.