Nosological status and definition of schizophrenia: Some considerations for DSM-V and ICD-11

Although dementia praecox or schizophrenia has been considered a unique disease entity for the past century, its definitions and boundaries have varied over this period. In this article, we examine the changing conceptualization of schizophrenia over the past 100 years and make some recommendations with regards to its definition in DSM-V and ICD-11.

We summarize clinical features of schizophrenia in terms of symptomatology, course, and outcome. We examine factors that lead to changing definitions of a disorder such as schizophrenia, with specific reference to the evolution of its definition from DSM-1 (American Psychiatric Association, Washington, DC, 1952) to the current DSM-IV-TR.

Efforts to elucidate the etiology and pathophysiology of schizophrenia have been hampered by its imprecise definition and continuing transformations in its conceptualization. The definition of schizophrenia, at any given time, has been influenced by available diagnostic tools and treatments, other clinical considerations, extant knowledge and scientific paradigms. It is now clear that schizophrenia does not represent a single disease with a unitary etiology or pathogenetic process. Despite limitations in the concept, however, alternative approaches thus far have been unsuccessful in better defining the syndrome of schizophrenia or its component entities.

Whereas changing definitions of schizophrenia might impede research into its nature and development of more effective treatments, only a better understanding of schizophrenia can lead to its more precise definition. We consider the implications of our observations for DSM-V and ICD-11 definitions of schizophrenia and summarize some emerging preliminary recommendations.