Related Experiment Video
Updated: Jul 16, 2026

Development of a Virtual Reality Assessment of Everyday Living Skills
Published on: April 23, 2014
Premorbid IQ varies across different definitions of schizophrenia
Annick Urfer Parnas1, Lennart Jansson, Peter Handest
1Cognitive Research Unit, University Department of Psychiatry, Hvidovre Hospital, DK-2650 Hvidovre;
Abstract:
The nature of the association between IQ and schizophrenia is still unclear. So far no study addressed this issue in relation to the breadth or scope of the very concept of schizophrenia. We examined the premorbid IQ in a polydiagnostic study with four classifications of schizophrenia: ICD-8/9, ICD-10, St. Louis and Flexible System-Wide. Only the ICD-10 schizophrenia patients exhibited a significantly lower premorbid IQ. There were suggestive differences between the four examined systems as well as between the ICD-10 paranoid and non-paranoid subtypes. Exploration of crucial diagnostic features of schizophrenia in relation to IQ revealed associations between low premorbid IQ and hallucinations as well as negative symptoms. It is concluded that premorbid IQ varies across different definitions of schizophrenia.
Related Concept Videos
Biological Causes of Schizophrenia
Genetic Factors in Schizophrenia
The genetic basis of schizophrenia is strongly supported by family and twin studies.
Intellectual Disability
Psychological and Sociocultural Causes of Schizophrenia
Schizophrenia
Biological Influences on Intelligence
Psychosis: Pathophysiology of Schizophrenia and Other Psychotic Disorders
Researchers have identified genetic factors that increase susceptibility to schizophrenia, underscoring the intricate interplay between genetics and environment in disease development. At the core of schizophrenia's pathophysiology is excessive dopaminergic neurotransmission within the...

