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Discuss issues in the classification and diagnosis of schizophrenia (24 marks)
The main tool of measurement to classify and diagnose schizophrenia is the Diagnostic Statistical
Manual (DSM-IV). One issue present is the tool's reliability which refers to the consistency of a
measuring instrument, such as DSM-IV. This can be measured in terms of whether two independent
assessors give similar scores (inter-rater reliability), or whether tests used to deliver the diagnoses
are consistent over time (test-retest).
Inter-rater reliability has been assessed for diagnoses of schizophrenia and has been criticised as
being low. Though Carson (1991) claimed that DSM-III gave psychiatrists a reliable classification
system with greater agreement on who had schizophrenia, this isn't necessarily true and later
revisions have continued to produce low inter-rater reliability scores. For example, Whaley (2001)
found only a small positive correlation of +0.11 between different raters.
In addition, cultural interpretations also pose a threat to the reliability of the diagnosis of
schizophrenia. Copeland (1971) gave a description of a patient showing clinical characteristics
associated with schizophrenia to 134US and 194UK psychiatrists.
Of the US psychiatrists, 69% diagnosed schizophrenia, whereas only 2% of the UK psychiatrists gave
the same diagnosis. This leads to suggest that the diagnostic criteria is ethnocentric because it
applies an emic construct when it is actually etic, therefore being culture biased because Copeland
found schizophrenia has an imposed etic which reduces the reliability between cultures.
In addition, the reliability of diagnosing schizophrenia is challenged through Rosenhan (1973) who
claimed that situational factors were more important in determining the ultimate diagnosis of
schizophrenia, rather than any specific characteristics of the person.
This was demonstrated through Rosenhan's `Being Sane in Insane Places' where various
psuedopatients presented themselves to psychiatric hospitals in the US claiming to be hearing voices
(a positive symptom of schizophrenia). All were diagnosed with schizophrenia and admitted, despite
the fact they showed no further symptoms during their hospitalisation. Throughout their stay, none
of the staff recognised they were normal and interpreted all their behaviour as being symptomatic
of schizophrenia- for instance waiting for dinner before the canteen opened was diagnosed as
characteristic of schizophrenia, though there was little else for them to do.
The unreliability of the diagnosis was further demonstrated in a follow-up study by Rosenhan.
Psychiatrists at several mental hospitals were told to expect psuedopatients over a period of
several months. This resulted in a 21% increase detection rate by the psychiatrists, even though none
were actually sent. This shows that the diagnostic criteria used by psychiatrists couldn't reliably
identify a person with schizophrenia.
Alternatively, validity refers to the extent that the classification system such as DSM measures what
it claims to measure. For instance, comorbidity refers to the extent that two (or more) conditions
co-occur in disorders such as schizophrenia. Therefore comorbidity is the extent to which the
condition is `real' and distinct.
One way to avoid the issue of comorbidity is to use first-rank symptoms of schizophrenia when
diagnosing (e.g. delusions and hallucinations) because Klosterkotter et al (1994) assessed 500
psychiatric admissions to Germany to determine whether positive or negative symptoms are more
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However, Bentall et al
(1988) claimed that many of the first-rank symptoms of schizophrenia are also found in other
disorders (such as depression and bipolar). This makes it difficult to separate schizophrenia as a
distinct disorder because there is crossover in symptoms; therefore schizophrenia is not a distinct
It may be more realistic to suggest that there is no discrete disorder as schizophrenia, but rather it's
an `umbrella term' encompassing a spectrum of psychotic symptoms.…read more