A plan for a Psychology essay.

1. To what extent can diagnosis be
reliable and valid?
Actually, I felt
fine before you
started
diagnosing me!
Bulimia
nervosa
Major depressive
disorder
Post-traumatic stress
disorder

2. Key phrases and words in title
In title Definition
To what
extent?
This is the central argument: how much is diagnosis valid and reliable, and
why; and how much is it not valid and reliable, and why?
Reliable As related to this question: inter-rater reliability is when different
psychiatrists or clinical psychologists agree on a diagnosis, using the same
diagnostic manuals. (Using different diagnostic manuals you are testing the
reliability of the manuals). Test-retest reliability is concerned with whether
the same person will received the same diagnosis on two different days.
Valid As related to this question: the main issue is if people with a certain
disorder are correctly diagnosed and those without the disorder are not
diagnosed. Construct validity is when a diagnosis has a predictive quality
and ties in with how the person behaves. The diagnostic test should be
measuring what it claims to be measuring. (i.e. a test for bulimia nervosa
should measure if a person has this disorder).
Diagnosis The procedure of labelling/identifying the disorder, for the purposes of
treatment. Usually through a formal standardized diagnostic interview.

3. Reliability and Validity

4. Brief Outline
Intro – define the terms and introduce the
argument: very difficult to diagnose psychological
disorders.
Content-
• Inter-rater reliability
• Test-retest reliability
• Construct validity (especially cross-culturally)
• Confirmation bias and validity
• Conclusion – only able to be reliable and valid to
a limited extent

5. The Plan (intro1)
Introduction: SET OUT THE ISSUE
Paragraph 1
• Define reliability (inter-rater and test-retest)
• Define validity (construct validity )
• Define diagnosis – examining signs (apparent
evidence) and symptoms (reported by patient) .
• Define the problem: reliable and valid diagnosing
is easier with physical illnesses than with mental
disorders – because many mental disorders do
not have a clear cause or clear symptoms of any
one disorder that are the same across patients.

6. The Plan (intro2)
• Particular problems associated with reliability and
validity:
• Reliability of diagnosis can only be guaranteed to the
extent that a classificatory system (OCD 10, DSM 5,
CCMD 3) is reliable and is used by different
psychiatrists and the same psychiatrist at different
times, to make the same diagnosis.
• Validity of diagnosis can only be shown to the extent
that to be valid a diagnosis has to be “correct”.
Construct validity – the test used must identify a real
pattern of symptoms, and apply a correct diagnosis, so
that the patient may be treated. This is even more
difficult than reliability of diagnosis

7. The Plan (Content1)
USE EMPIRICAL EVIDENCE
• Reliability of diagnosis greatly criticised in 1970s (see Cooper (1972) and
diagnosis in USA vs UK). Arguments are that it is better now, because of
regular modifications to the manuals. (Give examples – multi-axial
classifications, agreements between ICD-10 and DSM-5 etc.)
• Inter-rater reliability: But the classification systems merely represent
current understanding and there is still variation amongst them – Nicholls
et al (2000) and DSM-IV, ICD-10 and Great Ormond Street system). Inter-
rater reliability on 81 children with eating disorders (as diagnosed by the
GOS criteria) was the following: ICD-10 = 0.357; DSM-IV = 0.636; GOS =
0.879.
• So, two psychiatrists could barely agree, using the same criteria in the same
manual. The specialised manual for children had the best inter-rater
reliability. Suggests that the extent of reliability depends on the specificity
of the manual.

8. • Not only the classification systems that
determine the reliability of a diagnosis. The
psychiatrist’s role is vital.
• Test-retest reliability: Seeman (2007) – test-
retest reliability for schizophrenia. Initial
diagnosis of schizophrenia, especially in women,
was often changed as the psychiatrists got to
know their patients better. The extent of the
reliability of the first diagnosis is therefore
limited.
The Plan (Content2)

9. The Plan (Content3)
• Validity of diagnosis is particularly problematic when
considering construct validity. (There are differences in the
definitions of the same mental disorders between the
classification systems ICD-10, DSM 5 and the CCMD-3).
• See Szasz and also Laing (1960s and 1970s) for early
arguments that mental illness is a “social construction”,
with diagnosis relying on cultural, political, and/or social
context. Labelling is a form of control of those who do not
conform.
• The interpretation of the psychiatrists is also a problem for
validity of diagnosis. See Jenkins-Hall and Sacco (1991) for
an example of racial/ethnic bias in diagnosis. This suggests
that the diagnosis is not valid, even if the classification of
the disorder is.

10. The Plan (Content4)
• Therefore the extent of the validity of diagnosis depends on the
psychiatrist/clinical psychologist being able to apply the criteria and
correctly diagnose and treat the patient. As shown above (Jenkins-
Hall & Sacco) this is only possible if s/he does not subjectively
interpret the classifications in a biased fashion.
• Relate this to cross-cultural diagnosis as problematic - the
psychiatrist may not be familiar with the symptoms presented by
the patient as being relevant to a particular disorder and so may not
be able to arrive at a valid diagnosis (see Marsella 2003)
• Confirmation bias can give the appearance of validity to a diagnosis
when there is none: see Rosenhan (1973) – once pseudo-patients
were diagnosed, every behaviour they exhibited was interpreted
within the framework of the diagnosis, seeming to support its
validity. It was very difficult for them to leave the mental institution
by convincing the doctors that they were not suffering from a
disorder.

11. The Plan (Conclusion)
SUMMARISE THE ANSWER TO THE QUESTION
• Therefore, a diagnosis can only be reliable to the extent that the
classification system used is reliable and the interpretation of the
classification by the psychiatrist or clinical psychologist is reliable.
• Similarly, a diagnosis can only be valid to the extent that the
symptoms are correctly interpreted and if there is agreement
between the classification systems as to which particular disorder
this applies.
• Given the diversity of cultures presenting with symptoms, different
definitions in different classification systems, the fact that these are
interpreted in varying ways, and the presence of personal bias and
confirmation bias, a diagnosis can only be reliable and valid to a
very limited extent.

12. What did you notice?
1. Was the title referred to throughout?
2. How integrated was the critical thinking?
3. Were there markers like “therefore” “this
shows that”?
4. Was there a logical argument supported by
evidence?
5. Did the conclusion answer the question?