Transcript 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
payment
Techniques of diagnosis




Observation
Interview
Psychological tests (e.g. IQ tests)
Brain scans
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
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. DSM-IV-TR
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 voices.
 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 50.
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)
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