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Schizophrenia: Issues of RELIABILITY in Diagnosis & Classification
This normally comes up as a big 9+16 essay along the lines of ‘Discuss issues in the diagnosis &
classification of Schizophrenia’. If you learn the studies below then you’re most of the way there…
AO1 Issues in the Reliability of Diagnosis / Classification:
Classification system for mental disorders is DSM-IV (USA) and ICD-10 (UK & Rest of World).
In these books are symptoms of each disorder and how long they need to be present - and
with what severity - for the individual to be labelled with that particular condition. Each book
is updated periodically to try and improve the validity & reliability in light of new research etc.
A system of Classification is useful because:
 Mental health professionals may then have a better idea of what treatments will be
suitable for an individual, although this will often involve an element of trial and error
 It may help patients to come to terms with their disorder by being able to give their
problems a label
 Their structure can guide research; eg. similarities between patients can help to identify
the cause of a disorder, facilitate be of help in assessing the effectiveness of treatment.
A useful classification system needs to be reliable, ie. it must produce consistent results, so
that the professionals using it can agree on a classification for a particular patient. One
problem is that of differential diagnosis: being able to differentiate the symptoms of S from
other illness, both mental and physical.
AO2 Evaluation of Issues in the Reliability of Diagnosis / Classification:
1. Bhui et al. (l998) found that symptoms of S may be present in those with
Huntingdons chorea, brain tumour, epilepsy, multiple sclerosis and substance abuse,
especially LSD, ecstasy & amphetamines. They also report that there may be
difficulties in differentiating schizophrenia from mania and depression, both of which
may share symptoms
2. Rosenhan (1973) See KEY STUDIES factsheet. Basically proved that mental health
professionals are not always accurate in their diagnoses.
3. Beck (1967) Got 4 Psychiatrists to agree on how they’d apply DSM to diagnose S.
When presented with 153 ill individuals, they agreed on a diagnosis of S in only 54%
of cases.
4. Temerline (1970) Showed that psychiatrists who are making a diagnosis of
somebody’s mental health can be easily biased by the opinions of others, rendering
their opinion unreliable.
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Brookfield Psychology FactCard 4.1.2.0: Diagnosis & Classification of Schizophrenia
Schizophrenia: Issues of VALIDITY in Diagnosis & Classification
This normally comes up as a big 9+16 essay along the lines of ‘Discuss issues in the diagnosis &
classification of Schizophrenia’. If you learn the studies below then you’re most of the way there…
AO1: Issues in the Validity of Diagnosis / Classification:
Validity: refers to the meaningfulness and usefulness of the categories used. A valid system
for classifying & diagnosing Schizophrenia should use categories that refer to:
 a consistent pattern of symptoms
 a single aetiology
 an indication of treatment
 guidance as to the expected outcome
Within the area of mental illness, classification can have three forms of validity:
Aetiological validity: the same factors have caused the disorder in the diagnostic group. For
example, if a disorder is thought to be genetic, there should be a family history of the disorder
in everyone who is classified as having it. BUT, AO2:
 there are no clear causes for schizophrenia, so a classification tends to be symptombased rather than aetiology-based
 Patients do not come with symptoms that conform to tidy diagnostic categories, so a
decision has to be made in terms of which category provides the best fit
Concurrent validity: other symptoms, not part of the classification itself should be
characteristic of those diagnosed. For example, most people classified with schizophrenia
also have problems in personal relationships. BUT, AO2:
 there is a lot of variation between individuals given the same classification, particularly
in the case of schizophrenia (Costella, 1992)
Predictive validity: there should be similarities in the course of the disorder, with patients
suffering from it showing similar behaviour. In other words, a specific prognosis can be made
and the effects of treatment should be predictable. BUT, AO2:
 as there is often little in the way of a pathological basis for most psychiatric illnesses,
predictive validity is established through follow-up studies, but this is made difficult by
the inability to measure mental states accurately.
AO2: Evaluation of Issues in the Validity of Diagnosis / Classification:
Even if the classification system for Schizophrenia is reliable (in that clinicians consistently
agree on it) it may not be necessarily valid. This is because:
 mental disorders are by their nature harder to classify than physical illnesses
 there is often considerable overlap between conditions (eg. with Schizophrenia &
Biplolar Disorder) and it cannot be assumed that conditions are discrete
 many of the symptoms patients report are subjective, and the clinician is likely to lack
objective information, such as blood tests and X-rays etc, available to doctors
diagnosing a physical illness; classification depends entirely on symptoms
 the range of symptoms shown by people diagnosed as having schizophrenia is
extremely variable, so much so that two people with S may have totally different
symptoms
 for most physical illnesses the causes are known, making it relatively easy to check that
a diagnosis is correct. However, the causes of mental disorders are largely unknown
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Brookfield Psychology FactCard 4.1.2.0: Diagnosis & Classification of Schizophrenia
Schizophrenia: Issues of Diagnosis & Classification
KEY STUDIES: It’s worth learning all of these in detail. All exemplify well the
difficulty in getting accurate diagnoses from mental health professionals.
Reliability 1:
Reliability 2:
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Brookfield Psychology FactCard 4.1.2.0: Diagnosis & Classification of Schizophrenia
Reliability 3:
Rosenhan Evaluation:
 Perhaps the study really shows that psychiatrists cannot tell the difference between someone
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with a mental disorder and someone pretending to have a mental disorder, rather than an
inability to distinguish between a person with a mental disorder and one with no such disorder.
It’s worth noting that the pseudo-patients insisted on being admitted, which is, in itself, a sign
of serious mental disturbance, and that they claimed to hear voices, a symptom for which
there is no possibility of independent confirmation.
lt may also be that the psychiatrists involved in the study were more likely to diagnose a
healthy person as being ill rather than an ill person as being healthy erring on the side of
caution, given that it would be potentially dangerous to leave an ill person untreated.
There are clearly ethical problems here in that mental health staff were deliberately deceived
about the mental health status of patients, although it could be argued that deception was
necessary for the study to be viable.
More importantly, it is possible that in the follow-up study people with genuine mental health
problems who were identified as pseudo-patients did not receive the treatment they needed.
It has been claimed that if the same study were carried out today the pseudo-patients would
not be able to gain admission, as DSM-IV would not now diagnose them as schizophrenic. The
diagnostic criteria used nowadays are more detailed and precise than those used when
Rosenhan carried out his research. Wing et al. (1974) claimed that with DSM-IV the reliability
of classification is improved when a structured interviewing technique is used, which involves a
standardised diagnostic procedure with specific criteria and a computerised scoring program.
BUT… it really was an imaginative and ground-breaking study that put the issue of mental health diagnosis
under the microscope, and led to important reforms in how such patients were treated etc
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Brookfield Psychology FactCard 4.1.2.0: Diagnosis & Classification of Schizophrenia
Schizophrenia: Further Issues of Diagnosis & Classification
A few extra points for you to slip into your essay, should time allow…
 DSM and lCD found not to agree on S diagnosis, eg. Cooper (1972) found S
diagnosis twice as likely to be made in USA (using DSM), than by in London (using
ICD. BUT more recent versions much closer than before, so later research is less
prone to contamination as a result of schizophrenia being described in widely
disparate ways.
 Have even been cases of treatment guiding diagnosis, eg. a patient may be
classified as schizophrenic but not respond to the drugs used to treat S. If they
respond to drugs used to treat bipolar disorder the diagnosis can be changed to
bipolar disorder.
 It appears that problems of validity are inevitable in the classification of mental
disorders, perhaps giving the impression of the precision of a medical diagnosis, but
resting heavily on interpretation and inference. Eg. some doctors have been shown
to exhibit bias when providing a classification for different ethnic groups; Mukherjee
(1983) found that African-Americans were far more likely than white Americans to
be classified as schizophrenic, even when both groups presented with similar
symptoms
 Classification systems have not been rigorously tested on a UK African-Caribbean
population and so may not be accurate for this group. This kind of bias can also
work the other way For example; Lopez and Hernandez (1986) reported a clinician
as believing that blacks were more likely than whites to suffer from hallucinations,
so did not consider a classification of schizophrenia for a black person with
hallucinations.
 A further difficulty of this kind in making a valid classification may arise as a result
of communication difficulties between clinician and patient. Eg. Howes et al. (2007)
carried out a case study of a 26 year-old man who presented with low mood and
lack of motivation. He complained of feeling less sociable and finding it harder to
think. He was otherwise fit and healthy and there was no history of a recent stressor
that might have brought on his symptoms. He also used words in an unusual way
which he claimed was street slang, although it was not clear whether this was
indeed the case; it could instead have been a symptom of thought disorder, one of
the diagnostic criteria for schizophrenia. ln this kind of situation, it may be difficult
for a clinician, unfamiliar with street slang, to make a valid classification.
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Brookfield Psychology FactCard 4.1.2.0: Diagnosis & Classification of Schizophrenia