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1. Issues surrounding the classification and diagnosis of schizophrenia – including validity and reliability The biological model is the dominant approach to explaining…
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  • 1. Issues surrounding the classification and diagnosis of schizophrenia – including validity and reliability The biological model is the dominant approach to explaining and treating mental illness (psychopathology). This approach assumes that mental illness can be classified and diagnosed. There are two systems widely used in psychiatry; the International Classification System for Diseases (ICD) and the Diagnostic and Statistical Manual of Mental Disorders (DSM). The ICD was developed in Europe and the DSM was developed in America. The manuals are frequently revised and the UK is currently using the DSM-IV-TR. An ideal diagnostic system has certain characteristics; 1. The categories are mutually exclusive – they do not overlap 2. The categories are exhaustive – they cover the whole range of possible categories 3. Features of a disorder must be either present or absent – we can make yes/ no decisions based on the description 4. The system should be valid and reliable Keep these features in mind when looking at the issues surrounding the classification and diagnosis of schizophrenia. What are the benefits and drawbacks of using a classification system? Benefits of classification Disadvantages of classification
  • 2. Two issues which arise in the study of classification and diagnosis are cultural bias and socially sensitive research. Explain why. RELIABILITY Reliability in this context means the likelihood of different clinicians using the same system to arrive at the same diagnosis for the same patient. Early versions of the manuals were not very reliable. One problem was that key terms were not clearly defined and another was that clinicians used different techniques when interviewing and assessing patients. Consider the following famous study by Rosenhan. 'Sane in insane places' - Rosenhan's study 1973 ROSENHAN carried out two studies in U.S. psychiatric hospitals, to find out whether or not the medical staff could judge between mental normality and abnormality. In the first study eight ordinary people went to hospital admission departments claiming to hear voices saying EMPTY, HOLLOW and THUD; seven were admitted with a diagnosis of schizophrenia. In the second study a hospital was warned that some pseudopatients would try to be admitted. In fact there were none, but about 10% of the real patients were subsequently suspected of being fakes. This shows the difficulty in distinguishing between normality and abnormality. In the first study the pseudopatients, once admitted, reported experiencing depersonalisation and powerlessness, being ignored by nurses and psychiatrists. Everything they did was interpreted as a symptom of mental illness because that was what the medical staff expected to see. The studies raise some ethical concerns about deception. This study was conducted over 30 years ago. Since then manuals have been improved and diagnostic practise is very different. For example, categories and definitions are more detailed and operationalised and psychiatrists now use standardised interview schedules when assessing patients. Also the ICD and DSM have been bought in line with one another so they are now very similar. When classifying schizophrenia the major difference is that the DSM specifies that signs of disturbance must be present for at least six months, whereas the ICD requires that important symptoms are present for only one month.
  • 3. Reliability Despite the claims for increased reliability in the DSM-IV-TR there is still little evidence that DSM is routinely used with high reliability by psychiatrist. Whaley (2001) has found inter-rater reliability correlations in the diagnosis of schizophrenia as low as 0.11. Reasons for unreliability include the following; 1. Unreliable symptoms – it is possible to give individuals with totally different behaviours (different combinations of the key characteristics) the same diagnosis of schizophrenia. But do the patients have the same disorder or do have they different disorders with similar characteristics? 2. Only one of the characteristics is needed ‘if delusions are bizarre.’ Is it easy for clinicians to differentiate between ‘bizarre’ and ‘not bizarre?’ What level of inter-rater reliability was found amongst US senior psychiatrists when asked to distinguish between ‘bizarre’ and ‘not bizarre’ delusions? 3. Cultural differences in diagnosis – reliability is further challenged by the finding that there is massive variation in the diagnosis of schizophrenia between countries. Copeland et al gave a description of a patient to 134 US and 194 British psychiatrists. What % of US and British psychiatrists diagnosed schizophrenia? It is also worth remembering that psychiatrists in countries such as Pakistan, India and China use manuals which, although largely based on the ICM, exclude certain categories and include a category called neurasthenia (weakness of the nerves). The DSM has dropped this term and only includes it in the appendix for culture bound syndromes. This diagnosis will sometimes be used as a cover for schizophrenia or depression as a way of avoiding stigma. 4. The use of other diagnostic tools – along with the ICD and DSM clinicians use other diagnostic tools to help diagnose schizophrenia (e.g. St. Louis Criteria). The fact that other criteria have been developed makes research comparisons difficult. It also highlights the difficultly clinicians have when deciding what exactly they mean by the diagnosis of schizophrenia. If the categories are poorly defined and arbitrary, consistent diagnosis (reliable diagnosis) is likely to be low.
  • 4. VALIDITY If psychiatrist cannot decide who has schizophrenia (low reliability) then questions of what it actually is (validity) is undermined. Descriptive validity = Predictive validity = Validity in the diagnosis of schizophrenia is affected by the following factors; 1. Symptom overlap – some of the schizophrenic symptoms are found in many other disorders, such as depression and bipolar disorder. Ellason and Ross point out that people with dissociative identity disorder have more schizophrenic symptoms than people diagnosed as being schizophrenic! This affects the validity of the diagnosis. 2. The ICD and DSM have tried to overcome the problem of symptom overlap by proposing mixed disorder categories such as schizo-affective disorder or post-psychotic depression. The validity of these, however, needs to be questioned. 3. Variability in symptoms and response to treatment – the variety in combinations of symptoms and response to treatments has led to the development of sub-types. Name four of these sub-types: However, the validity of these sub-types has been questioned. For example, many diagnosed with undifferentiated schizophrenia will be recategorised later when new symptoms develop. 4. Self-fulfilling prophecy – what is meant by this? How would it affect the validity of the schizophrenic diagnosis? 5. Predictive validity – can the diagnosis of schizophrenia allow a psychiatrist to predict outcome and response to treatment?
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