Reliability And Validity In The Diagnosis And Classification Of Schizophrenia

Question 1

Define diagnostic reliability

Answer 1

Diagnostic reliability means that a particular diagnosis must be repeatable. It refers to the level of agreement in diagnosis by different psychiatrists across time and cultures.

Question 2

What is test-retest reliability in terms of a reliable diagnosis?

Answer 2

A mental health professional must give the same diagnosis for the same patient at different points in time.

Question 3

What is inter-rater reliability in terms of a reliable diagnosis?

Answer 3

Different mental health professionals must arrive at the same diagnosis for the same patient.

Question 4

Name the study that questions the unreliability of diagnosis

Answer 4

Rosenham’s study

Question 5

Describe and evaluate Rosenham’s study into the unreliability of diagnosis

Answer 5

8 ‘pseudo patients’ who were actually psychologically healthy made appointments at different hospitals in the USA. They all complained of hearing an unfamiliar voice, using the words ‘thud’, ‘hollow’ and ‘empty’.

7 out of 8 were diagnosed with schizophrenia. Once in hospital they behaved normally and asked to be released. It took between 7 and 52 days to be released. Throughout the stay nine of the hospital recognised that they were normal. In fact, normal behaviour was seen as ‘abnormal’.

This study highlights the unreliability of diagnosis and how it is possible for misdiagnosis. In this case, non-schizophrenic people were diagnosed with schizophrenia.

EVALUATION:

This study was carried out a long time ago under the DSM-11 so the data may no longer be valid. Most people agree that the reliability of diagnosis for schizophrenia has improved over time with improvements in the classification systems; however there is still a worrying level of misdiagnosis.

Question 6

What study researched test-retest reliability?

Answer 6

Read et al

Question 7

Describe and evaluate Read’s study

Answer 7

Read et al showed a concordance rate of only 38% for test-retest reliability. In other words, when a person is diagnosed with schizophrenia when a test is first administered, there is only a 38% chance that they will be diagnosed again on a retest sometime later.

This suggests that there is a low test-retest reliability which is a weakness as it shows that there is a high level of misdiagnosis of schizophrenia.

Question 8

What study researched inter-rated reliability?

Answer 8

Cheniaux et al

Question 9

Describe and evaluate Cheniaux’s study

Answer 9

Cheniaux et al had two psychiatrists independently diagnose 100 patients using both the DSM and the ICD classification systems. Inter-rater reliability was poor, with one psychiatrist diagnosing 26 with schizophrenia according to the DSM and 44 according to the ICD. The other psychiatrist diagnosed 13 according to the DSM and 24 according to the ICD.

This shows that there is poor inter-rather reliability between psychiatrists which is a weakness for the diagnosis of schizophrenia.

Question 10

What is validity?

Answer 10

Validity refers to the validity extent to which we are measuring what we intend to measure.

Question 11

What is validity in terms of diagnosis?

Answer 11

In terms of diagnosis it refers to the extent to which schizophrenia is a unique disorder with characteristic signs and symptoms that are separate from other disorders.

Question 12

What is validity in terms of classification?

Answer 12

In terms of classification it refers to the extent to which classification systems such as the DSM-V and ICD-10 measure what they claim to measure - in this case schizophrenia

Question 13

What is predictive validity?

Answer 13

If diagnosis is valid it will predict the outcome of the disorder in terms of how well a person will recover.

Question 14

What is a problem with the validity of diagnosis?

Answer 14

A problem with the validity of diagnosis is that there is no evidence that people with schizophrenia share the same outcomes. The prognosis for patients diagnosed its schizophrenia varies with about 20% recovering to their previous level of functioning, 10% achieving lasting significant and lasting improvement. And about 30% showing some improvement with occasional relapses.

A diagnosis of schizophrenia, therefore, had low predictive validity - some people never appear to recover, whereas many do. The predictive validity of schizophrenia diagnosis can also be argued to be low because different suffered experience such a wide range of symptoms.

Question 15

Name the 4 other threats to validity

Answer 15

• Gender bias
• Co-morbidity
• Symptom overlap
• Culture bias

Question 16

When does gender bias in the diagnosis of schizophrenia occur?

Answer 16

It is said to occur when the accuracy of diagnosis is dependent on the gender of an individual.

Question 17

Discuss gender bias in terms of the validity of diagnosing schizophrenia

Answer 17

The accepted belief was that males and female were equally vulnerable to the disorder, however, since the 1980s men have been diagnosed with schizophrenia more often than women. Some argue that this is because psychiatrists misapply diagnostic criteria to women. This may be simply that men are more genetically vulnerable to developing schizophrenia than women. However, gender bias in diagnosis seems more likely.

It appears that female schizophrenics tend to function better than male schizophrenics - being more likely to work and have good family relationships. This better functioning could explain why women have not been diagnosed with schizophrenia when men with similar symptoms have. Under-diagnosis may be due to symptoms being masked by good interpersonal functioning or because their higher functioning makes the case seem too mild for a diagnosis.

This suggests that diagnosis is influenced by the gender of a person.

Question 18

What is co-morbidity?

Answer 18

Co-morbidity refers to the occurrence of two or more conditional measures together (e.g. Schizophrenia and depression). If conditions are frequently diagnosed together it calls into question the validity of classifying the two disorders separately because they might actually be one condition.

Question 19

Describe the evidence/research done into co-morbidity

Answer 19

Schizophrenia is commonly diagnosed with other conditions. In a review of diagnosis, Buckley et al concluded that around half of patients with a diagnosis of schizophrenia also have a diagnosis of depression (50%) or substance abuse (47%). OCD also occurs in 23% of patients

Question 20

Why does this pose a problem for the validity in terms of diagnosis?

Answer 20

In terms of diagnosis - if 50% of patients with schizophrenia are also diagnosed with depression, maybe clinicians are bad at telling the difference between the two conditions

Question 21

Why does this pose a problem in terms of classification?

Answer 21

In terms of classification- if severe depression is similar to schizophrenia, they might be better classified as a single condition.

Question 22

What is symptom overlap? + evaluation

Answer 22

Symptom overlap is when a disorder shares a lot of the same symptoms with another disorder. In the case of schizophrenia, both sz and bipolar disorder include positive symptoms such as delusions and negative symptoms such as avolition. Under the ICD-10 a patient might be diagnosed as schizophrenic with these symptoms, however many would receive a diagnosis of bipolar disorder according to the DSM-V.

This calls into question the validity of classifying these two disorders separately as they may not be two disorders but one, and also questions the validity of the accuracy of diagnosis for these two conditions.

Question 23

Discuss culture bias in terms of validity

Answer 23

Research suggests that there is significant variation between countries when it comes to diagnosing schizophrenia which suggests that culture has an impact on the diagnostic process.

African Americans and English people of Afro-Caribbean origin are several times more likely that white people to be diagnosed with schizophrenia. Given that the rates in Africa and the West Indies are not particularly high, this is almost certainly not due to genetic vulnerability.

Question 24

Who does the low rates of schizophrenia diagnosis in Africa and the West Indies but high rates in England indicate culture bias?

Answer 24

• One reason is that positive symptoms such as hearing voices may be more acceptable in African cultures because of cultural beliefs in communication with dead ancestors and thus people are more ready to acknowledge such experiences.
• when reported to a psychiatrist from a different culture, these experiences are likely to be seen as bizarre and irrational
• white psychiatrists may over-interpret symptoms and distrust the honesty of black people during diagnosis.

Question 25

What does the over diagnosis of schizophrenia in Black British and Americans suggest about the validity of diagnosis?

Answer 25

It suggests that the validity of diagnosis is poor because it is confounded by cultural belief and behaviour in patients, or by racist distrust of black patients on the behalf of mental health practitioners.

Question 26

Jamaican-born Agwe has been referred to a psychiatrist because he has been told that he had recently heard his dead grandfather talking to him.

With reference to the terms ‘positive symptoms’ and ‘hallucinations’ explain why Agwe might receive a diagnosis of schizophrenia.

Answer 26

Positive symptoms of schizophrenia are additional symptoms beyond those of normal experience. One of these is auditory hallucinations in which someone hears a voice that no one else can, like Agwe hearing his dead grandfather talking to him. So Agwe may receive a diagnosis of schizophrenia because he is displaying the positive symptom of auditory hallucination.

Question 27

Jamaican-born Agwe has been referred to a psychiatrist because he has been told that he had recently heard his dead grandfather talking to him.

How might issues of culture bias affect this potential diagnosis?

Answer 27

Agwe was born in Jamaica and it is their cultural belief that their ancestors communicate with them . This experience is not regarded as particularly abnormal for Agwe’s cultural group. If Agwe is not displaying any other symptoms of schizophrenia this means it is unlikely that he would receive a diagnosis of schizophrenia, though a psychiatrist who was unaware of his background might regard the voice as a definite symptom.