Classification and diagnosis

• Schizophrenia= severe mental disorder where contact with reality and insight are impaired.
• Positive symptoms

  = Additional experiences beyond those of ordinary existence.

  • Hallucinations
  • Delusions
• Hallucinations= unusual sensory experience that have no basis in reality or are distorted perceptions of things that are there.
• Delusions= irrational beliefs. Eg: believe they are someone else.
• Negative symptoms

  = Loss of usual experience.

  • Speech poverty
  • Avolition
• Speech poverty= changes in speech pattern like frequency and quality
• Avolition= loss of motivation and reduced activity levels.
• Classification

  ICD-10 = negative symptoms

  DSM-5 = positive symptoms
• Good reliability 

  = Good consistency on inter-rater reliability and test retest reliability.

  • Osorio reported good diagnosis of schizophrenia in 180 individuals, using DSM-5.
  • Inter rater reliability was +.97 and test retest reliability was +.92
  • So diagnosis is consistently applied.
• Low validity

  = Assess validity using criterion validity.

  • Cheniaux study- 2 psychiatrists independently assess same 100 clients using ICD-10 and DSM-5
  • 68 were diagnosed under ICD and 39 under DSM system.
  • So schizophrenia is either over or under diagnosed
  • So criterion validity is low.
• Counterpoint

  Osorio study reported that there was excellent agreement between clinicians when using two measures to diagnose schizophrenia both derived from DSM system.

  So means that criterion validity for diagnosing schizophrenia is actually good provided it takes place within a single diagnostic system.
• Co-morbidity

  = Occurance of two disorders together.

  • Eg: schizophrenia and personality disorder
  • Study found that about half of those diagnosed with schizophrenia also had a diagnosis of depression or substance abuse.
  • So schizophrenia may not exist as a distinct condition
  • Questions validity of classifying the disorders separately.
• Gender bias in diagnosis

  = More men than women have received a diagnosis of schizophrenia.

  • Suggests there is bias in diagnosis with women being under diagnosed due to better interpersonal functioning.
• Culture bias in diagnosis

  = African Caribbean British were 9 times more likely to be diagnosed then white British, maybe because norms in African Caribbean communities are misinterpreted by white clinicians.
• Symptoms overlap

  = Symptoms of schizophrenia like bipolar disorder overlap, both conditions involve delusions and avolition.

  Suggests that schizophrenia and bipolar disorder may not be two different conditions but variations of a single condition.

  Schizophrenia is hard to distinguish from bipolar disorder.

  • Makes diagnosis and classification difficult.