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Explain how reliability and validity affect the diagnosis of mental health and illness.

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Explain how reliability and validity affect the diagnosis of mental health and illness. Rosenhan's study uncovered weaknesses in the process of diagnosis using the DSM-11. The study shows that the method used for diagnosis was reliable because participants went to a range of different hospitals, and so therefore different psychologists treated them. Each participant presented the psychologist with the exact same symptoms, and all of the psychologists diagnosed them as schizophrenic, showing 100% reliability for diagnosis. The diagnosis is considered reliable because more than one psychologist gave the same diagnosis for the same symptoms. This study supports the idea, that if the classification system is reliable, then diagnosis will be 100% correct. However the study showed that the process of diagnosis used by the psychologists was low in validity, because all of the participants were misdiagnosed. Each psychologist diagnosed the pseudo patients as schizophrenic, when actually they were all faking. The diagnosis system was found to be low in validity, which resulted in patients being misdiagnosed. ...read more.


This study again highlights the problems in the DSM-11 classification system. The study supports the suggestion raised by the Rosenhan's study, that the diagnosis system is low in validity, because may of the diagnosticians were influenced, which resulted in them giving the wrong diagnosis. Beck et al found that agreement on diagnosis for 153 patients was only 54%, which is a lot less than the 100% diagnosis for the Rosenhan study. This study therefore shows that the system is low in reliability, as different psychologists could not agree on the same diagnosis. This may be due to vague criteria for diagnosis or inconsistencies in the techniques used to gather data. The sample used in this study is much greater than the one used in the Rosenhan study. The results from this study goes against the Rosenhan study, therefore suggesting that the small sample size may have affected the overall results, and actually the DSM-11 classification is unreliable which cause different psychiatrists to diagnose the same patient with a different disorder. ...read more.


Di Nardo et al found that reliability for some disorders can be quite high, whereas reliability for others is much lower. This suggests that the classification system is biased towards some disorders, because of problems with interpreting what the patient was feeling. If a patient was misdiagnosed, then they would be treated for the wrong disorder, and would not be helped. The DSM was able to correct this fault in their classification system to prevent problems in interpretation, and so to increase overall reliability for all disorders, and hopefully result in more correct diagnosis. Much of the research into the reliability and validity of the DSM-11 classification system, was conducted a number of years ago. The diagnostic procedures have now improved, and we now have the DSM-IV-TR-VI, which is much more reliable and valid. These studies therefore cannot show how reliable and valid the new classification system is. Psychiatrists now generally agree on a diagnosis. These studies have therefore benefited many patients, as now it is less likely that they will be misdiagnosed because the classification system is unreliable and low in validity. ...read more.

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