Discuss the validity and reliability of diagnosis

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Discuss the validity and reliability of diagnosis

• By Mr Daniel Hansson

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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

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Techniques of diagnosis

• Observation
• Interview
• Psychological tests (e.g. IQ tests)
• Brain scans

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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

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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

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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)

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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

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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

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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

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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

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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

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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)

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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)

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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.

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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)

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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