Issues of reliability and validity in classifying and diagnosing schizophrenia


Discuss issues of reliability and validity in the classification and diagnosis of schizophrenia (24 marks) 

AO1 (describe) in pink

AO2 (evaluate) in green

valid diagnosis

  • when a psychiatrists diagnosis is accurate and correct.
  • evidence for invalid diagnosis of schizophrenia: Rosenhan (1970)- asked 8 pseudo patients to visit various mental hospitals complaining of hearing a voice in their head that said 'thud'. all 8 pseudo patients were diagnosed as schizophrenic, even though they only had one symptom of schizophrenia. The mental hospitals in question asked for more pseudo patients to be sent when they found out about the first experiment. the hospitals thought 41 were sent, as they diagnosed this many as schizophrenic, however no pseudo patients were sent in this follow up study.
  • this shows that the diagnosis of both normal people and actual schizophrenics was invalid as the incorrect diagnosis was given. this lead to the creation of the DSM III, which gives a more detailed classification of schizophrenia, hopefully solving this problem.

reliable diagnosis

  • when two or more psychiatrists agree with each other concerning a patients diagnosis and symptoms
  • evidence for unreliable diagnosis of schizophrenia: Whaley (2001)- found that 2 psychiatrists who were studying reports of possible schizphrenic patients only agreed on a diagnosis 11% of the time.
  • this shows that diagnosis of schizophrenia can be unreliable as psychiatrists find it hard to agree on a diagnosis most of the time. therefore dispite improvements after rosenhan's study there are still issues.

reasons for poor reliability of the diagnosis of schizophrenia

 different cultures

  • copeland- asked 134 american psychiatrists and 194 british psychiatrists to diagnose possible schizophrenics and found that american psychiatrists said 69% were schizophrenic whereas the british said only 2% were schizophrenic.
  • shows that culture can effect the liklihood of being diagnosed as schizophrenic, therefore reducing the reliability of diagnosis as people from different culture have different views on what a schizophrenic is.

co-morbidity (having more than one mental illness at a time)

  • e.g. a patient may have symptoms of depression as well as the negative symptoms of schizophrenia such as alogia and affective flattening. It would be hard to diagnose a patient as schizophrenic as depression can hide other symptoms of schiziophrenic, such as dilusions.
  • in order to treat the patient we have to be sure they have 2 different illnesses or they may recieve the wrong treatment

different books to diagnose schizophrenia

  • DSM-V is used in UK and America, but other books are used elsewhere which define schizophrenia differently, so a diagnosis may be different and therefore unreliable. china use the CCMD and europe use ICD.
  • this means that diagnosis can be unreliable as two different psychiatrists from different countries may diagnose a patient differently as they wee trained by using differrnt books, so each have different views on what a schizophrenic is.

no objective test such as a blood test

  • no way to be certian of a diagnosis, so it is hard for psychiatrists to agree as it is their own opinion

range of types of schizophrenia


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