Schizophrenia: Disease Entity, Disease Entities, or Domains of Psychopathology

Schizophrenic patients, regardless of diagnostic concept and criteria applied, show a marked variability in age and type of onset, premorbid or early morbid adjustment, signs and symptoms, treatment response, and course of illness. Extensive between-subject variability is also observed in risk factors (e.g., genetic, gestational and birth complications, and season of birth) and associated biological and psychological features. Although individual variability contributes to differences in clinical manifestations, the observed clinical heterogeneity also underscores a conceptual issue of profound importance. Is schizophrenia a single disease, multiple diseases with certain core manifestations im common, or a varying combination of multiple pathophysiological processes, each leading to a different aspect of the syndrome?