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Discuss the validity and reliability of diagnosis

Discuss the validity and reliability of diagnosis

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Discuss the validity and reliability of diagnosis

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  1. Discuss the validity and reliability of diagnosis By Mr Daniel Hansson

  2. The purpose of diagnosis • To identify groups of similar sufferers so that psychiatrists and psychologists may develop explanations and methods to help those groups • Billing purposes. The government and many insurance companies require a diagnosis for payment

  3. Techniques of diagnosis • Observation • Interview • Psychological tests (e.g. IQ tests) • Brain scans

  4. DSM-IV-TR • The classification system used in the United States • Lists more than 250 mental disorders • The diagnosis of one individual is based on five dimensions

  5. The five dimensions of DSM-IV-TR • Axis I: The major diagnostic classification, e.g. major depressive disorder, anorexia • Axis II: Related to developmental and personality disorders (e.g. autism, anti-social personality) • Axis III: Physical and medical conditions that may worsen the disorder (e.g. brain injury, drug abuse, viruses) • Axis IV: Psychosocial stressors, all stressful events that may be relevant to the disorder (e.g. poverty, divorce, loss of job) • Axis V: Global assessment of functioning. Rates the highest level of social, occupational and psychological functioning on a scale of 1 (persistent danger) and 90 (good in all areas) currently and during the last year

  6. Reliability and validity of diagnosis • Reliability of diagnosis: Will different diagnosticians using the same classification system arrive at the same diagnosis? • Validity of diagnosis: Does the person diagnosed have real symptoms with a real underlying cause? (the illness is not socially constructed, the person is not faking)

  7. Reliability of diagnosis • The reliability of earlier systems for diagnosis, e.g. DSM-II, was very poor, but it has been improved in revisions of the systems, e.g. DSM-IV-TR

  8. Reliability of diagnosis • Beck (1962): Agreement between two psychiatrists on diagnosis for 153 patients was 54 %. This was due to vague criteria for diagnosis and different ways of psychiatrists to gather information • Cooper et. al. (1972): When shown the same video clips, New York psychiatrists are twice as likely to diagnose schizophrenia than London psychiatrists. London psychiatrists were twice as likely to diagnose mania or depression than New York psychiatrists

  9. Reliability of diagnosis • Di Nardo (1993): Two clinicians separately diagnosed 267 people seeking treatment for anxiety and stress disorders. They found higher reliability for obsessive compulsive disorder but lower reliability for major depression

  10. Validity of diagnosis • There is a tendency of practitioners of overemphasizing dispositional rather than situational causes of behaviour when diagnosing patients (Fundamental attribution error) • The labelling of patients with certain disorders may affect the practioners perceptions of them (compare with researcher bias), patients may act the label that has been given to them (self fulfilling prophecy). The label itself may simplify a problem that is highly complex • People may fake mental illness in order to avoid punishment (The insanity defense) • Szaz 1967: Many disorders may be culturally constructed. If the biological causes of the mental disorder are known, the individual may be diagnosed with mental disorder (the mental illness criterion). If there is no biologically underlying cause of the disorder, it is better to claim that the individual has problems with living or adapting • There are significant individual differences for mental disorders. An individual may have multiple mental disorders

  11. Validity of diagnosis • Rosenhan (1973): 8 sane people could get admitted to mental hospitals merely by claiming to hear voices. • Rosenhan (1973): When a teaching hospital was told to expect pseudo-patients, they suspected 41 out of 193 genuine patients of being fakers

  12. Validity of diagnosis • Temerline (1970): Clinically trained psychiatrists was influenced in their diagnosis by hearing the opinion of a respected authority. (expert influence). Participants watched a video-taped interview of a healthy individual. The authority claimed, even though the person only seemed to be neurotic (distress where behaviour is not outside social norms, patient has not lost touch with reality) he was actually psychotic (behaviour is outside social norms, loss of touch with reality)

  13. Validity of diagnosis • Chapman & Chapman (1967): Beginning clinicians observed draw-a-person test drawing randomly paired (unknowingly to participants) with symptom statements of patients. Although the relationship between symptoms and drawings were absent, participants rated a high associative strength between symptom and drawing characteristics (e.g. paranoia and drawing big eyes)

  14. Validity of diagnosis • Lipton & Simon (1985): 131 patients were randomly chosen at a New York hospital. Initially there were 89 patients diagnosed with schizophrenia, eventually only 16. Initially, there were 15 diagnosed with depression, eventually there were 50.

  15. Evaluation • There is a large amount of research supporting the view that the reliability and validity of diagnosis are poor. This is due to many reasons, e.g. a possible social construction of mental illness, poor diagnostic tools, the possibility of faking, social influence, errors in attribution by practitioners and labeling • There are significant individual and cultural differences for the symptoms of mental disorders. An individual may have multiple mental disorders • A wrong diagnosis may lead to a social stigma (an ethical issue)

  16. Counter argument • There are methodological problems with the studies on validity and reliability (researcher bias, generalisability, ecological validity) • Revised diagnostic tools are higher in reliability than earlier versions, e.g. DSM-IV-TR • Many people do seek help voluntarily for disorders (which may mean that the disorder is valid) • The reliability of diagnosis is high for some disorders, e.g. obsessive compulsive disorder • There are many similarities of disorders across cultures • Diagnostic systems do not classify people, but the disorders that they have