reliability and validity of diagnosing schizophrenia

• Diagnostic reliability= means that the diagnosis of schizophrenia must be repeatable- clinicians must be able to reach the same conclusions at different points in time (test-retest)
• • Test retest and inter-rater reliability is measured with aa correlation called a Kappa score. Kappa score of 1 = perfect inter-rater agreement (0.8 is accepted)
  • In DSM-V trials Regier et al fond the diagnosis of schizophrenia has a kappa score of 0.46
  • Whaley - found that inter-rater reliability kappa scores for schizophrenia diagnosis was a s low as 0.11
• • Critic of the DSM-V argue the diagnosing categories are biased towards 1 gender 
  • Broverman et al (1970) - found that clinicians in the US equated mentally healthy adult behaviour as mentally healthy male behaviour. As a result, there's a tendency for women to be perceived as less mentally healthy. - androcentric 
• • Mojtabi & Nicholson (1995)- asked 50 senior psychiatrists in the US to differentiate between bizarre and non-bizarre delusions and produced kappa scores of around 0.4, forcing researchers to conclude that classification of symptoms lack sufficient reliability to distinguish between schizophrenic and non-schizophrenic patients.
• Rosenhan conducted a field experiment where normal people presented themselves to psychiatric hospitals claiming they could hear unfamiliar voices in their heads - they were all admitted to the hospital and diagnosed with schizophrenia - throughout their stay, none of the staff realised that these people were not actually displaying symptoms of schizophrenia - suggests the diagnosis of schizophrenia is not valid or reliable
• • Cultural bias in schizophrenia diagnosis's- Copeland (1971) - gave 134 US and 194 British psychiatrists a description of a patient - 69% of us clinicians diagnosed schizophrenia compared to 2% of British clinicians
• • Symptom overlap - both schizophrenia and bipolar involves symptoms such as delusions and avolition. Ellason & Ross (1995) identified that those with D.I.D have more symptoms of schizophrenia than those with schizophrenia.