Subtypes Of Schizophrenia

The classical subtypes of schizophrenia relate back to Kraepelin and Bleuler. They are defined by the predominant symptomatology at the time of evaluation.

The first three classical subtypes of schizophrenia (dementia paranoides, hebephrenia and catatonia) were described as separate illnesses until Krae-pelin brought them together under the name dementia praecox. Together with schizophrenia simplex or simple schizophrenia, which was introduced by Bleuler, Kraepelin's paranoid, hebephrenic and catatonic subtypes formed Bleuler's group of schizophrenias. Over the years, additional subtypes, such as latent, undifferentiated, or residual schizophrenia, have been added to the four main types included in Bleuler's original description; some of the subtypes have been renamed, and others have been redefined using slightly different criteria.

In 1974, Tsuang and Winokur [92] suggested that patients with paranoid schizophrenia had fewer psychomotor symptoms and that they were characterized by later onset of illness, less seclusiveness, less distractibility, fewer psychomotor symptoms, a higher incidence of marriage, more children, and less disruption of social and familial relationships. In a review of 32 studies related to intellectual functioning, attention, memory, language, visuo-spatial, and motor functioning, Zalewski et al [93] did not find, however, any consistent differences between patients with paranoid and patients with non-paranoid schizophrenia.

In an extensive recent review concerning the classical subtypes of schizophrenia, McGlashan and Fenton [94] have examined the validity of the paranoid, hebephrenic (disorganized), catatonic, simple and undifferentiated subtypes of schizophrenia. The authors review data from familial and genetic studies, subtype stability studies, outcome studies, and neurological and neuropsychological investigations. They conclude that the studies of the last decade lend overall support for the validity of the paranoid, and, albeit with less force, for the validity of the disorganized and undifferentiated subtypes. According to the same review, catatonia is not specific to schizophrenia, but can still characterize a subtype of this disorder. Finally, there is evidence to support the validity of simple schizophrenia.

In 1989, Black and Boffeli [95] provided a historical overview of simple schizophrenia, reviewed its modern successors, and provided recommendations and diagnostic criteria for its inclusion in DSM-IV. The category has been included in DSM-IV, although with different criteria and only in an appendix listing diagnostic categories which need further study.

New approaches to the subtyping of schizophrenia include the type I-type II or positive-negative dichotomy and the proposition of a dimensional model.

Crow [12] proposed a typology for schizophrenia which is based on the positive -negative symptom dichotomy. According to this author, the two types may reflect two aetiologically and prognostically distinct pathological processes. The main symptoms of the positive syndrome (or type I) are hallucinations and delusions. This type may be associated with biochemical imbalance involving dopaminergic overactivity. The main symptoms of the negative syndrome (or type II) are affective flattening and poverty of speech. This type may be associated with structural or anatomical abnormality reflected in ventricular enlargement and cortical atrophy.

In an appendix on criteria sets provided for further study, the DSM-IV [5] introduces a dimensional alternative to the classical subtypes of schizophrenia that have been described above. This alternative is based upon a three-factor dimensional model. The three factors included in the model are a psychotic, a disorganized and a negative one. The psychotic factor includes delusions and hallucinations; the disorganized factor includes disorganized speech, disorganized behaviour, and inappropriate affect; and the negative factor comprises affective flattening, alogia and avolition. According to the authors of DSM-IV, there are studies which suggest that the severity of symptoms within each of the three factors tends to vary together, both cross-sectionally and over time, whereas this is less true for symptoms across factors.

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