Reliability and validity

• Comorbidity


  Where the person has two or more conditions which can lead to symptom overlap
• Symptom overlap


  Symptoms may not be specific to a certain disorder and can be found within multiple disorders
• Gender bias


  Diagnostic criteria is applied differently to males and females
• Culture


  There is a tendency to over diagnose members of other cultures as having schizophrenia
• How can the reliability of the classification systems be assessed?


  1. Consistency
  2. Diagnostic reliability
  3. Inter-rater reliability
• Consistency


  Refers to the consistency of a classification system to assess symptoms
• Reliability

  Diagnostic reliability means a diagnosis must be repeatable (test-retest reliability)
• Inter-rater reliability


  Different clinicians must reach the same conclusions
• Cheniaux (2009)


  • 2 psychiatrists diagnose 100 patients independently using the DSM and ICD
• Cheniaux's (2009) findings


  • One psychiatrist diagnosed 26 patients using DSM and 44 using ICD
  • The other diagnosed 13 using the DSM and 24 using the ICD
  • Poor inter-rater reliability
• Rosenhan (1973)


  • Ppts had an appointment under a fake name
  • Said they were hearing voices
  • When admitted, ppts stopped simulating symptoms
  • In wards, ppts engaged with others as they would colleagues
  • Discharged when staff saw fit
• Rosenhan's (1973) findings


  Stays lasted from 7-52 days with the mean being 19 days
• Criterion validity

  Do different assessment systems arrive at the same diagnosis for the same patient
• 


  Rosenhan (1973) found that in a follow-up study, the same doctors declined genuine patients with schizophrenia because they believed they were part of the same deception
• Longenecker et al indicate that since the 1980s, men have been diagnosed with schizophrenia more frequently than women because of a gender bias
• Longenecker et al suggested that women operate at a higher level of functioning, have better interpersonal skills, are more likely to work, and maintain more stable family relationships than men, which can mask their symptoms
• African-Americans and English people with afro-Caribbean origin are more frequently diagnosed with schizophrenia that white people, even though this bias is not seen in Africa- cultural bias