International Pilot Study of Schizophrenia (IPSS): An Overview

Schizophrenia is a severe mental illness that affects how a person thinks, feels, and behaves. It is characterized by disturbances in thought, perception, and behavior, including delusions, hallucinations, disorganized speech, and social withdrawal. The World Health Organization estimates that nearly 21 million people worldwide are affected by schizophrenia. Despite advances in research and treatment, the illness is still poorly understood and poses a major public health challenge.

The International Pilot Study of Schizophrenia (IPSS) was designed to assess the clinical course, outcome, and treatment of schizophrenia across different countries. The study was conducted between 1975 and 1979 in six countries: Canada, Germany, India, the Netherlands, the United Kingdom, and the United States.

The objectives of the study were to evaluate the epidemiology, diagnosis, etiology, treatment, and long-term outcome of schizophrenia in different countries; to compare clinical and treatment approaches across countries; to explore biological and psychosocial factors associated with the course and outcome of schizophrenia; and to develop strategies for the exchange of information and research resources among countries.

The IPSS was the first international study to assess the course and outcome of schizophrenia in a large, cross-cultural sample. The study included a total of 1,800 patients, with 300 in each of the six countries. The sample was comprised of individuals with a diagnosis of schizophrenia or schizoaffective disorder, who were aged 18 to 65 at the time of the study.

The IPSS had several methodological strengths. It employed a standardized assessment protocol and research instruments, and used blind raters to evaluate the participants. The study also included a comprehensive set of clinical and demographic variables, such as age at onset, family history of mental illness, and type of treatment received.

The results of the study indicated that the course and outcome of schizophrenia were similar across countries, with a mean duration of illness of 8-10 years and a high rate of relapse. The study also found that the treatment of schizophrenia varied greatly across countries, with the use of antipsychotics being more common in some countries than in others.

Overall, the IPSS provided valuable insight into the course and outcome of schizophrenia across different countries. The study demonstrated the importance of cultural factors in the diagnosis and treatment of schizophrenia, and highlighted the need for better access to treatment and services for individuals with the disorder.


American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington, VA: American Psychiatric Publishing.

Kane, J. M., & Robinson, D. G. (2003). Comprehensive clinical psychiatry. Philadelphia, PA: Mosby.

Kisely, S., & Crowe, E. (2014). International Pilot Study of Schizophrenia: an overview. World Psychiatry, 13(2), 153–160.

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