Discuss the reliability and validity issues surrounding the classification and diagnosis of schizophrenia

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Discuss the reliability and validity issues surrounding the classification and diagnosis of
schizophrenia ( 24 marks)
Schizophrenia is said to be a serious mental disorder characterised by a lack of contact with
reality and severe disruptions in psychological functioning. Researchers suggest that
schizophrenia isn't a single mental disorder and can be split into various subtypes. These
include; catatonic schizophrenia, paranoid schizophrenia, hebephrenic schizophrenia,
undifferentiated schizophrenia, post schizophrenic depression, residual schizophrenia and
simple schizophrenia. Since there are various subtypes, it means that all schizophrenics
don't display the same behaviour making the classification and diagnosis very difficult.
ICD-10 is one of the main classification systems in use to diagnose people with
schizophrenia and other mental illnesses. ICD-10 distinguishes between two different
groups. The first group consists of thought control, delusions of control/ influence/ passivity,
hallucinatory voices and other persistent delusions for example believing themselves to be a
religious leader. The second group consists of persistent hallucinations, incoherent or
irrelevant speech, catatonic behaviour and negative symptoms. According to ICE 10, there is
a minimum requirement for at least one of the symptoms listed under the first group or two
listed from the second group to be present for a period of at least one month to be
diagnosed with schizophrenia.
DSM IV is another main classification system. According to this manual, there are criteria to
meet for a person to be diagnosed with schizophrenia. They include the patient
experiencing at least two symptoms for one month (same symptoms listed in the ICD
groups), social/occupational disturbance and continuous disturbance over six months with
one month of active symptoms.
There are many strengths and weaknesses with the classification and diagnosis of
schizophrenia which revolve around reliability and validity.
One of the issues surrounding reliability is inter rater reliability. There have been many
studies surrounding the reliability of diagnosis's using the DSM IV. Previous studies showed
that there was a problem with inter rater reliability. However Carson (1991) claimed that
DSM III had fixed the problem once and for all. Nevertheless, recent studies for example
(Whaley 2001) found inter rater reliability correlations is as low as +11 meaning that
psychiatrists often have difficulty agreeing on diagnosis. A study to show that the diagnosis
and classification of schizophrenia has low inter rater reliability is Rosenhans famous study,
in which normal healthy people presented themselves in psychiatric hospitals. Due to them
claiming they heard words such as `empty', `thud' and `hollow', they were diagnosed as
having schizophrenia and were admitted. None of the hospital staff realised they were
actually normal.
On the other hand, a strength surrounding reliability of the classification and diagnosis of
schizophrenia is that it receives high test retest reliability. Measuring cognitive functioning is

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Wilks et al administered two alternate forms of the RBANS test to
schizophrenics over intervals varying from 1 ­ 134 days. The test retest reliability was fairly
high at 0.84. Prescott et al also supports this as they analysed the test retest reliability of
several measures of attention and information processing in 14 schizophrenic patients. The
performance on these measures was constant over a 6 month period.
An issue revolving around validity is co morbidity.…read more

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