Reliability and Validity

• reliability if the consistency of the measuring technique

  • in schizophrenia diagnosis, it means the consistency of diagnoses between psychiatrists
• validity is the extent to which we are measuring what we intend to

  • if the diagnosis is accurate
• inter rater reliability is reached when 2 or more psychiatrists make the same diagnosis of an individual independent of each other
• Cheniaux et al

  • presented 100 patient cases to 2 psychiatrists
  • using the DSM and ICD criteria
  • found that inter-rater reliability was poor
  • both were more likely to diagnose people with schizophrenia using the ICD compared to the DSM
  • poor reliability is a weakness of the diagnosis of schizophrenia
• a consequence of problems with reliability and validity of classification and diagnosis of schizophrenia is that patients may not receive the appropriate treatment
• Rosenhan - Being sane in insane places

  • conducted a study that supported the lack of validity in a schizophrenia diagnosis
  • rosenhan recruited 8 people to go into a psychiatric hospital, reporting that they were hearing voices
  • when admitted, they acted normally
  • the shortest stay was 7 days, longest 52 and average 19 days.
• Rosenhan further

  • told institutions about his results
  • they told him to send more pseudopatients and said that they would spot them
  • hospitals reported that 42 patients were suspected of being fakes, 19 of them being diagnosed by 2 members of staff.
  • in fact, Rosenhan did not send any pseudopatients
  • they were misdiagnosing real patients with real illnesses
• comorbidity is when someone experiences multiple illnesses at once. The symptom for these may overlap, meaning they may be mistaken for one another. For example, depression and schizophrenia. There is questioning around if some comorbid illnesses with schizophrenia should be classed as their own separate illness.
• Buckley et al

  • concluded that approximately half of patients with a schizophrenia diagnosis also have a depression diagnosis
  • substance abuse - 47%
  • PTSD - 29%
  • OCD - 23%
  • It is thought that the high suicide rate for schizophrenia may be due to comorbid depression rather than the actual schizophrenia itself
• Symptom overlap is when there is an extensive of symptoms between two distinct disorders e.g bipolar disorder and schizophrenia both involve delusions and avolition.
• Under ICD, a patient might be diagnosed with schizophrenia however many of the same patients would receive a bipolar disorder diagnosis under the DSM