Schizophernia - classification and diagnosis

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DSM criteria for schizophernia

Characteristic symptoms: two or more fo the following for a significant time during a one month period: delusions, hallucinations, disorganised speech, disorganised or catatonic behaviour, negative symptoms: flattening or alogia

these can be present but can not be the result of drugs etc

Social/occuptaional dysfunction: since the disturbance period, for a significant time, work life or personal life must be affected

Duration: continuing signs of disturbance for at least six months, with one month of symptoms

Exclusion of mood disorders: bipolar or depression, as examples must not have occured during the period

Exclusion of known organic causes: no drugs can not be taken during the disturbance

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Diagnostic Criteria - Positive

positive symptoms are those that appear to add something to the personailty:

  • delusions: bizzare belifes that seem real to a person with schizophernia when in fact they are not. sometimes these delusions can be paranoid
  • experiences of control: the thought that your mind/body is being controlled by an external force e.g aliens
  • hallucinations: bizzare unreal perceptions of the environment that can be auditory, visual, olfactory or tactile
  • disordered thinking: the feeling that thoughts have been inserted or withdrawn fom the mind and that people can hear them
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Diagnostic Criteria - Negative

negavtive symptoms are those that appear to show a loss of normal functions

  • affective flattening: a reduction in the range of emotional expression e.g eye contanct
  • alogia: poverty of peech
  • avoiliton: having no goal behaviour e.g going to school
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Issues with the reliablity and validity


  • when using the DMS to diagnosis schizophernia there have been low correlations to show that it is used effectively to diagnosis. these inter-rater reliablity correlations when diaganosing schziophernia have been as low as 0.11
  • positive symptoms have been shown to better diagnosis then negative
  • psychiatrists were asked to differentiate between bizzare and non bizzare behaviours and found that they produced inter-rater reliablity of only around 0.40 lacking sufficent evidence for the DSM to be called reliable


  • Researchers developed the first-rank symptoms which are believed to distinguish schizophernia from other disorders
  • however DID is shown to have more schizophernic symptoms than schizophernia!
  • little evidence to show that schizophernics share the same outcomes.
  • 20% recovering to previous level of functioning 10% significant and lasting improvement 30% some improvement with intermittent relapses
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