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Discuss the validity and reliability of diagnosis


Discuss the validity and reliability of diagnosis By Mr Daniel Hansson The purpose of diagnosis To identify groups of similar sufferers so that psychiatrists and ... – PowerPoint PPT presentation

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Title: Discuss the validity and reliability of diagnosis

Discuss the validity and reliability of diagnosis
  • By Mr Daniel Hansson

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

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

  • The classification system used in the United
  • Lists more than 250 mental disorders
  • The diagnosis of one individual is based on five

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

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)

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.

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

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

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

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

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)

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)

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

  • 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)

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
  • The reliability of diagnosis is high for some
    disorders, e.g. obsessive compulsive disorder
  • There are many similarities of disorders across
  • Diagnostic systems do not classify people, but
    the disorders that they have
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