Discuss Issues Relating to Reliability and Validity Surrounding the Classification and Diagnosis of Schizophrenia. (16 Marks)

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  • Discuss Issues Relating to Reliability and Validity surrounding the Classification and Diagnosis of Schizophrenia (16 Marks)
    • Reliability
      • Definition - Consistency
        • Inter-rater reliablity (the extent to which assessors  agree on each other's assessments) is an important  measure of reliability
          • When it comes to diagnosis of schizophrenia or other mental health disorders this means the extent to which clinicians arrive at the same diagnosis for the same patients.
            • Study: Cheniaux et al (2009) Got two psychiatrists to independently diagnose 100 patients using both ICD and DSM  criteria.
              • Findings: Inter-rater reliability was poor. One psychiatrist diagnosed 26 with schizophrenia according to the DSM and 44 according to the ICD. This pootr reliability is a weakness of diagnosis of schizophrenia.
    • Validity
      • Definition -  Accuracy, the extent  to which we are measuring what we want to measure.
        • There are many validity issues to be acknowledged when diagnosing schizophrenia.
          • Criterion Validity  is a way of assessing the validity of  a diagnosis. It determines whether different assessment systems arrive at the same diagnosis for the same patient.
            • From Cheniaux et al's study it's clear that schizophrenia is more likely to be diagnosed using the ICD than the DSM.
              • This suggests  that schizophrenia is either over-diagnosed in the ICD  or under-diagnosed in the DSM. EIther way this  is poor validity and a weakness of  the diagnosis of schizophrenia.
    • Co-Morbidity
      • Definition- The phenomenon that two or more conditions occur together.
        • If the two or more conditions occur together frequently this calls the diagnosis and classification of both conditions into question  because what appears to be two conditions may be one.
          • Supporting Study: Peter Buckley et al (2009)  Found that around 1/2 of patients with a diagnosis of schizophrenia also have a diagnosis of depression (50%) or substance abuse (47%). Post-traumatic stress disorder also occurred in 29% of cases and OCD in 23%.
            • This is an issue for both diagnosis and classification.
              • In terms of diagnosis 1/2 of the patients have diagnosis of depression so therefore it could be down to human error - not being able to easily distinguish between the two conditions.
              • In terms of classification it may be that severe depression looks like schizophrenia and vice versa. These may be seen as a single condition.
                • This is a weakness of the diagnosis and classification of schizophrenia.
    • Symptom Overlap
      • Definition: When two conditions have the same or similar symptoms
        • Example: Both Schizophrenia and Bipolar Disorder involve positive symptoms such as delusions and negative symptoms like avolition.
          • This affects both diagnosis and clasification.
            • Under ICD criteria someone may be diagnosed as schizophrenic however, under the DSM they might be diagnosed with bipolar disorder.
              • This is unsurprising given the overlap of symptoms . The DSM even suggets that bipolar disorder and schizophrenia might not be two seperate conditions.


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