Discuss validity and reliability of
diagnosis
Diagnosis
Diagnosis within abnormal
psychology means identifying
and classifying abnormal
behavior on the basis of
• symptoms,
• the patients’ self-reports,
• observations,
• clinical tests
• other factors such as
information from relatives.
Discuss validity and reliability of diagnosis
Why Diagnose?
• Diagnosis involves
matching the results of
the psychological
assessment with
classification systems
such as DSM-V.
• The purpose of
diagnosis is to find a
treatment for the
patient and to make a
prognosis.
Discuss validity and reliability of diagnosis
Reliability of diagnosis
Discuss validity
and reliability of
diagnosis
You have learned the symptoms of
over thirty disorders……..
• You are going to try to
diagnose behavior.
• Use the sheets given.
• You SHOULD use your
notes!
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Discuss validity and reliability of diagnosis
Behavior 1
Behavior 2
Behavior 3
Behavior 4
Behavior 5
Behavior 6
Behavior 7
Behavior 8
Behavior 9
Discuss validity and reliability of diagnosis
Reliability of diagnosis
• Reliability in diagnosis
means that clinicians
should be able to reach
the same correct
diagnosis consistently if
they use the same
diagnostic procedure.
• This is called inter-judge
reliability.
How can we increase reliability?
• Reliability can be improved if
clinicians use standardized
clinical interview schedules,
which define and specify sets
of symptoms to look for.
• But the individual psychiatrist
must still make a subjective
interpretation of the severity
of the patient’s symptoms.
• The introduction of diagnostic
manuals has increased
reliability of diagnosis over
the year even though the
manuals are not without
flaws.
Discuss validity and reliability of diagnosis
Cooper et al. (1972)
The US-UK Diagnostic Project
• The aim of the study was
to investigate reliability of
diagnosis of depression
and schizophrenia.
• The researchers asked
American and British
psychiatrists to diagnose
patients by watching a
number of videotaped
clinical interviews.
Discuss validity and reliability of diagnosis
Cooper et al. (1972)
The US-UK Diagnostic Project
• The British psychiatrists
diagnosed the patients
in the interview to be
clinically depressed
twice as often.
• The American
psychiatrists diagnosed
the same patients to be
suffering from
schizophrenia twice as
often.
Discuss validity and reliability of diagnosis
Cooper et al. (1972)
The US-UK Diagnostic Project
• The results indicated that
the same cases did not
result in similar diagnosis
in the two countries.
• This points towards
problems of reliability as
well as cultural
differences in
interpretation of
symptoms and thus in
diagnosis.
Discuss validity and reliability of diagnosis
Validity of diagnosis
Discuss validity and reliability of diagnosis
Validity of diagnosis
• Validity of diagnosis refers to
receiving the correct
diagnosis.
• It is much more difficult to
provide a correct diagnosis
and give a prognosis for a
psychological disorder than
for a physical disorder
because it is not possible to
observe objective signs of
the disorder in the same way.
Discuss validity and reliability of diagnosis
Validity of diagnosis
• The DSM-V manual does
not include etiology but
only symptoms.
• Sometimes patients have
symptoms that relate to
different psychological
disorders so it can be
difficult to make a valid
diagnosis.
Discuss validity and reliability of diagnosis
Discuss validity and reliability of diagnosis
Rosenhan (1973)
On being sane in insane places
Aim:
• To test reliability and
validity of diagnosis in a
natural setting. Rosenhan
wanted to see if
psychiatrists could
distinguish between
“abnormal” and “normal”
behavior.
Discuss validity and reliability of diagnosis
Rosenhan (1973)
Procedure:
• This was a covert
participant observation
with eight participants
consisting of five men and
three women (including
Rosenhan himself).
• Their task was to follow
the same instructions and
present themselves in 12
psychiatric hospitals in
the USA.
Discuss validity and reliability of diagnosis
Rosenhan (1973)
Results:
• All participants were
admitted to various
psychiatric wards and all
but one were diagnosed
with schizophrenia.
• The last one was
diagnosed with manic
depression.
Discuss validity and reliability of diagnosis
Rosenhan (1973)
• All pseudo-patients
behaved normally while
they were hospitalized
because they were told
that they would only
get out if the staff
perceived them to be
well enough.
Discuss validity and reliability of diagnosis
Rosenhan (1973)
• The pseudo-patients
took notes when they
were hospitalized but
this was interpreted as
a symptom of their
illness by the staff.
• It took between 7 to 52
days before the
participants were
released.
Discuss validity and reliability of diagnosis
Rosenhan (1973)
• They came out with a
diagnosis
(schizophrenia in
remission) so they were
“labeled”.
Discuss validity and reliability of diagnosis
Rosenhan (1973)
Follow Up
• A follow-up study was
done later where the
staff at a specific
psychiatric hospital were
told that impostors would
present themselves at
the hospital and that they
should try to rate each
patient whether he or
she was an impostor.
Discuss validity and reliability of diagnosis
Rosenhan (1973)
Follow Up
Of the 193 patients:
• 41 were clearly identified
as impostors by at least
one member of the staff
• 23 were suspected to be
impostors by one
psychiatrist
• 19 were suspected by one
psychiatrist and one staff
member.
Discuss validity and reliability of diagnosis
Rosenhan (1973)
Follow Up
There were no impostors.
Discuss validity and reliability of diagnosis