Psychology Schizophrenic Disorders
Angus W. MacDonald, Ansam El Shaikh, Craig Moodie, Andrew Poppe, Ian Ramsay, Krista Wisner
  • LAST REVIEWED: 09 November 2017
  • LAST MODIFIED: 26 February 2013
  • DOI: 10.1093/obo/9780199828340-0105


While allusions to psychoses in the West date back to ancient Greek medicine and literature, the modern concept of schizophrenia is generally attributed to the German psychiatrist Emil Kraepelin (b. 1856–d. 1926). His description of schizophrenia as a syndrome composed of a diverse collection of seemingly unrelated symptoms that tended to co-occur across patients forms the basis for our modern diagnosis. According to the Diagnostic and Statistical Manual of the American Psychiatric Association (DSM-IV-TR), the diagnosis of schizophrenia requires two or more of the following manifestations of psychosis: delusions; hallucinations; disorganized speech; disorganized or catatonic behavior; or negative symptoms, such as lacking normal emotional responses to events, lacking normal levels of motivation, or a reduced flow of speech. To reduce the variety of people diagnosed with the disorder, the criteria also include a minimum duration and rule-outs for other conditions. These criteria will be changed very little in the forthcoming revision of the DSM (DSM-V). From Kraepelin’s early work to current diagnostic systems, schizophrenia has always been acknowledged to have varied cases within the disorder, as well as many cases that fall outside the diagnosis but that appear to be related to the construct. These include bipolar affective disorder with psychotic features and schizotypal personality disorder, which form part of a “schizophrenia spectrum.” We sometimes speak of schizophrenic disorders, rather than schizophrenia as a monolithic entity, to acknowledge this ambiguity and the possibility that people may have symptoms as a result of different causes. After a general introduction, this article is organized around different facets of the disorder: Causes, Brain Cells and Chemistry, Pathology, Neural and Behavioral Functioning, and Treatment.

General Overviews

While the modern construct of schizophrenia is attributed to Kraepelin 1971 (originally published 1919), Bleuler 1950 (originally published 1911) is an early contribution that is still recognized as prescient and relevant to understanding the importance of cognitive impairments as part of the disorder. Both works also provide important details about patients’ behavior from an era before modern antipsychotics, and speak to its prominence among those with serious mental illness during that era. They cannot provide, as McGrath, et al. 2008 can, an account of the widespread nature of the illness and how that prevalence varies across populations. About half a century after the delineation of the disorder, Meehl 1962 hailed a new era of schizophrenia research. Subsequently, research would be less driven by psychoanalytic concepts and more grounded in genetics and falsifiable hypotheses. However, progress in understanding schizophrenia has been slower than any of these early authors would have predicted, in part due to the tremendous variety of cases. Subtypes of schizophrenia, such as paranoid and catatonic, have been found to be unproductive. Researchers now commonly use several dimensional factors along which symptoms can vary, as summarized by Peralta and Cuesta 2001. A related approach, codified by Gottesman and Gould 2003, has been to look for markers and mechanisms further from the expression of the illness and closer to its causes. Another result of this slow progress is that researchers have broadened their investigations into the nature of schizophrenia to include many diverse fields. Two recent projects have therefore endeavored to draw together the diverse threads of research. The first of these (MacDonald and Schulz 2009) is written in the context of a special section of contemporary theories of the causes of schizophrenia, whereas the second (Tandon, et al. 2008) initiates a series of articles by the authors that attempts to rank all findings in schizophrenia on a series of criteria. These readings compose an entry point into the subsequent sections where additional aspects of the disorders are unpacked.

  • Bleuler, E. 1950. Dementia praecox or the group of schizophrenias. Translated by J. Zinkin. New York: International Univ. Press.

    Original work published in 1911. Swiss psychiatrist Eugen Bleuler (b. 1857–d. 1939) is credited with coining the term schizophrenia. This monograph is dedicated not only to its diagnosis but to understanding its causes and subtypes.

  • Gottesman, I. I., and T. D. Gould. 2003. The endophenotype concept in psychiatry: Etymology and strategic intentions. American Journal of Psychiatry 160.4: 636–645.

    DOI: 10.1176/appi.ajp.160.4.636

    Highly cited reference for the “endophenotype” approach in modern psychiatry. This approach acknowledges that many psychiatric disorders, including schizophrenia, have a complex genetic etiology that interacts with environmental factors in ways that are not understood. This paper summarized an approach to studying this problem in a more sophisticated way, and laid out criteria for determining which measurable variables shed the most light on the causes of schizophrenia-spectrum disorders.

  • Kraepelin, E. 1971. Dementia praecox and paraphrenia. Translated by R. M. Barclay. Huntington, NY: Robert E. Krieger.

    Original published in 1919. Kraepelin trained many psychiatrists and, through his frequently revised textbook, influenced many more. He differentiated schizophrenia, which he called dementia praecox, from manic depression, a distinction that remains both central to diagnosis and controversial.

  • MacDonald, A. W., and S. C. Schulz. 2009. What we know: Findings that every theory of schizophrenia should explain. Schizophrenia Bulletin 35.3: 493–508.

    DOI: 10.1093/schbul/sbp017

    A committee- and Internet-based effort to distill the primary findings of the schizophrenia literature into a condensed set of facts about the disorder and the construct for the purpose of comparing theories. This paper also serves as the introduction to a special section allowing for the comparison of competing theories. The process of developing this list can be observed in more detail on the Schizophrenia Research Forum website What We Know . . . What We Don’t Know About Schizophrenia.

  • McGrath, J., S. Saha, D. Chant, and J. Welham. 2008. Schizophrenia: A concise overview of incidence, prevalence, and mortality. Epidemiologic Reviews 30 (November): 67–76.

    DOI: 10.1093/epirev/mxn001

    This article provides an overview of three systematic reviews of the incidence, prevalence, and mortality of schizophrenia. The authors found that, contrary to many opinions, the incidence and prevalence of schizophrenia is highly variable depending on location. (Abstract available online.)

  • Meehl, P. E. 1962. Schizotaxia, schizotypy, schizophrenia. American Psychologist 17:827–838.

    DOI: 10.1037/h0041029

    Presidential address to the American Psychological Association reintroducing the construct of schizotypy as phenotype associated with the genetic liability to schizophrenia. Among other things, this work spurred new ways to think about the heterogeneity of patients, invigorated the search for indicators of unexpressed genetic liability (see Gottesman and Gould 2003), opened up research on schizotypy and its diagnosis, and ushered out the psychoanalytic idea that mothers’ nurturing behaviors caused psychosis. Meehl’s hypothesis that a dominant gene causes schizophrenia is discredited, but the idea of a specific cause underlying schizophrenia remains in many current theories.

  • Peralta, V., and M. J. Cuesta. 2001. How many and which are the psychopathological dimensions of schizophrenia? Issues influencing their ascertainment. Schizophrenia Research 49:269–285.

    DOI: 10.1016/S0920-9964(00)00071-2

    Unfortunately, and despite various schemes for subtyping patients, the heterogeneity of patients and their symptoms has been difficult to systematize. One of the most recognizable approaches today has been work to group symptoms using factor analyses, which tends to identify three factors, including positive (e.g., delusions and hallucinations), negative (e.g., blunted emotions and reduced speech), and disorganized speech and behavior. Mania and depression are two additional factors that are commonly observed in such studies.

  • Tandon, R., M. S. Keshavan, and H. A. Nasrallah. 2008. Schizophrenia, “Just the facts”: What we know in 2008; Part 1: Overview. Schizophrenia Research 100.1–3 (March): 4–19.

    DOI: 10.1016/j.schres.2008.01.022

    One of a series of publications by the authors in which they sift through a very large schizophrenia literature to determine which findings are most robust and which findings identify schizophrenia most specifically.

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