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Issues surrounding reliability and
validity in the classification and
diagnosis of schizophrenia
Psychopathology (schizophrenia)
AQA A A2 Psychology…read more

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Reliability and validity
· a reliable diagnosis are those which get the same
diagnosis when 2 or more psychiatrists diagnose a
· Whaley- found that 2 psychiatrists who were
studying reports of possible schizophrenic patients,
only agreed on the diagnosis 11% of the time. This
shows that diagnosis of schizophrenia can be
unreliable as psychiatrists find it hard to agree most
of the time…read more

Slide 3

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Reliability and validity
· A valid diagnosis is then the psychiatrists diagnosis is
accurate and correct
· Rosenhan- asked 8 pseudo patients to visit various mental
hospitals complaining of hearing a voice in their head that
said `thud'. Found that all 8 pseudo patients were
diagnosed as schizophrenic. A follow up study then involved
the original mental hospitals who asked to be sent more
pseudo patients so they could diagnose which ones were
schizophrenic. The hospitals thought 41 were sent where
in fact none were sent. This shows that diagnosis of both
normal people and real schizophrenics can be inaccurate.
This led to the creation of the DSM III which is more
detailed and should improve diagnosis.…read more

Slide 4

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Problems with miss diagnosis
· Culture- Copeland- asked 134 American psychiatrists
and 194 British psychiatrists to read some
descriptions of possible cases of schizophrenia and to
diagnose patients they think to have schizophrenia.
Found that American psychiatrists said 69% of
patients where schizophrenic but the British
psychiatrists said only 2% were schizophrenic. This
shows that culture can influence reliability of
diagnosis. Therefore the culture we are brought up in
can effect the likelihood of a diagnosis and the
reliability of a diagnosis even when the same books
are used.…read more

Slide 5

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Problems with miss diagnosis
· Co-Morbidity- this is when a patient suffers from 2
or more mental illnesses. This makes it hard to get a
reliable diagnosis as one illness can hide the symptoms
of the other. For example, a patient may show signs
of depression as well as the negative symptoms of
schizophrenia such as alogia and avolition. Therefore
it can be hard to diagnose a patient as schizophrenic
as depression an hide its symptoms. In order to treat
a patient we have to be sure they have 2 different
illnesses as they may receive the wrong treatment…read more

Slide 6

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Problems with miss diagnosis
· Books- several different books are used to define
schizophrenia and therefore diagnose patients. DSM-
IV is used to diagnose schizophrenia in the UK and
America. Other countries use different books. China
uses CCMD and Europe uses ICD. This means that
because different books are used to define
schizophrenia, patients can be diagnosed differently
depending on where they are from. Therefore
diagnoses can be unreliable as two different
psychologists may have different views on to what
extent a patient has schizophrenia as they were
trained with different books, so each can have a
slightly different idea of what schizophrenia is.…read more

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