Reliability & validity in diagnosis & classification

• Reliability - the consistency of measurements
• Validity - measures what it's supposed to
• Kappa score - measures inter-rate reliability
• Diagnosis of schizophrenia has a kappa score of 0.46
• Cultural differences of reliability of schizophrenia:

  • When given the description of a patient, 69% of US psychiatrists diagnosed him with schizophrenia, only 2% of british psychiatrists did
  • Hearing voices is influenced by cultural environments, African patients reported positive voices whereas US patients reported violent & hurtful
• Validity of diagnosis of schizophrenia:

  • Gender bias - DSM is based off males
  • Symptom overlap - many schizophrenia symptoms are found in other disorders
  • Co-morbidity - multiple conditions occur simultaneously in a patient
• Validity of diagnosis of schizophrenia :

  • Gender bias
  • Symptom overlap
  • Co-morbidity
• Reliability of Schizophrenia AO3:

  • ❌ Lack of inter-rate reliability - 0.11 correlation. Rosenhan study
  • ❌ Unreliable symptoms - only ‘bizzare delusions‘ are required for a diagnosis. US psychiatrists had an inter-rate reliability of 0.4 for which delusions are bizarre
• Validity of schizophrenia AO3:

  • ✅ Research support for gender bias - male psychiatrists are more likely to diagnose males with schizophrenia than diagnose women - influenced by gender of patient & clinician
  • ❌ Consequences of co-morbidity - patients receive a lower standard of medical care
  • ❌ Differences in prognosis - some people never recover from the disorder