Schizophrenia: Reliability and validity in diagnosis and calssification

Question 1

What are the 2 issues regarding the classification and diagnosis of SZ?

Answer 1

Reliability and validity

Question 2

What is meant by reliability for SZ?

Answer 2

Refers to the consistency of a measuring instrument like a questionnaire to assess the severity of their SZ symptoms.

Question 3

Define diagnostic reliability.

Answer 3

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 4

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

Answer 4

Different mental health professionals must arrive at the same diagnosis for the same patient. It is measured by a statistic called kappa score. A score ranging from 1 indicates perfect inter-rater agreement, and a score of 0 indicates zero agreement. In the DMS-V field trials, the diagnosis of schizophrenia got a score of only 0.46.

Question 5

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

Answer 5

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

Question 6

Name the study that questions the unreliability of diagnosis

Answer 6

Rosenham’s study

Question 7

Describe Rosenham’s study into the unreliability of diagnosis

Answer 7

• 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 the 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.

Question 8

What are the cultural variations in diagnosing schizophrenia? (2 studies)

Answer 8

• Copeland (1971) gave 134 US and 194 UK psychiatrists a description of a patient, 69% of US people were diagnosed with schizophrenia but only 2% of UK ones did. Shows that diagnosis is not reliable across cultures
• Luhrmann et al (2015) interviewed 60 Ghanaian, Indian and US schizophrenics about the voices they heard. Many African and Indian patients stated that the voices were ‘playful’ and positive whereas none of the US ones did and instead stated they were hateful. This study showed that ‘the harsh violent voices so common in the west may not be an inevitable feature of schizophrenia’ therefore questioning the validity of the diagnosis.

Question 9

What are 3 factors influencing validity in diagnosing schizophrenia?

Answer 9

• Gender bias
• Symptom overlap
• Co-morbidity

Question 10

How does gender bias influence the diagnosis of schizophrenia?

Answer 10

• This is where the accuracy of the diagnosis is dependent on the gender being diagnosed usually because of gender-biased diagnostic criteria or clinicians basing their judgements on stereotypical beliefs about a gender
• Broverman et al (1970) found US clinicians equated mentally healthy ‘adult’ behaviour with mentally healthy ‘male’ behaviour, therefore there was a tendency for women to be perceived as less mentally healthy

Question 11

How does symptom overlap influence the diagnosis of schizophrenia?

Answer 11

• Where symptoms of one disorder are also found in others e.g. feelings of grandiosity and inflated self-esteem being both a symptom of schizophrenia and bipolar disorder.
• This means that it’s difficult to accurately diagnose schizophrenia as clinicians may notice two symptoms of another disorder yet will diagnose schizophrenia as they are listed as schizophrenic symptoms in the DSM-V.

Question 12

What did psychologists research about symptom overlap?

Answer 12

Ellason and Ross (1995) point out that people with dissociative identity disorder (DID) actually have more schizophrenic symptoms than people diagnosed with schizophrenia.

Most people diagnosed with schizophrenia have sufficient symptoms of other disorders that they could also receive at least one other diagnosis. (Read, 2004)

Question 13

How does co-morbidity influence the diagnosis of schizophrenia?

Answer 13

The presence of two or more psychological disorders that occur together, leads to confusion over which condition is being diagnosed. It raises problems of validity, as if disorders always occur together, schizophrenia may not be a separate disorder. For example, schizophrenia and depression.

Question 14

What did psychologists research about co-morbidity?

Answer 14

Psychiatric comorbidities are common among patients with schizophrenia. These include substance abuse, anxiety and symptoms of depression.

Buckley et al (2009) estimate that co-morbid depression occurs in 50% of patients, and 47% of patients also have a lifetime diagnosis of co-morbid substance abuse.

A meta-analysis by Swets et al (2014) found that at least 12% of patients with schizophrenia also fulfilled the diagnostic criteria for OCD and about 25% displayed significant obsessive-compulsive symptoms.

Question 15

A03: Validity

Answer 15

+ Research support for gender bias
- The consequences of co-morbidity
- Differences in prognosis

Question 16

A03: Reliability

Answer 16

+ A comment on cultural differences in the diagnosis of schizophrenia
- Lack of inter-rater reliability
- Unreliable symptoms

Question 17

A03: Validity: Research support for gender bias

Answer 17

Loring and Powell (1988) randomly selected 290 male and female psychiatrists to read two case vignettes of patients’ behaviour. They were then asked to offer their judgement on these individuals using standard diagnostic criteria. When the patients were described as males or no information was given about their gender, 56% of the psychiatrist gave a diagnosis of schizophrenia. However, when the patients were described as female, only 20% were given a diagnosis of schizophrenia. Interestingly, this gender bias was not as evident among the female psychiatrist, suggesting that diagnosis influences not only the gender of the patient but also the gender of the clinician.

Question 18

A03: Validity: The consequences of co-morbidity

Answer 18

A number of studies have examined single co-morbidities with schizophrenia, but these studies have usually involved only relatively small sample sizes. By contrast, a US study looked at nearly 6,000,000 hospital discharge records to calculate comorbidity rates. Psychiatric behaviour-related diagnosis accounted for 45% of comorbidity. However, the study also found evidence of many co-morbid non-psychiatric diagnoses. Many patients with a primary diagnosis of schizophrenia are also diagnosed with medical problems including hypothyroidism, asthma, hypertension and type 2 diabetes. The authors concluded that the very nature of the diagnosis of the psychiatric disorder is that patients tend to receive a low standard of medical care, which in turn adversely affects the prognosis for patients with sz.

Question 19

A03: Validity: Differences in prognosis

Answer 19

In the same way that people diagnosed as schizophrenic rarely share the same symptoms, likewise, there is no evidence that they share the same outcomes. The prognosis for patients diagnosed with schizophrenia varies with about 20% recovering their previous level of functioning, 10% achieving significant and lasting improvement, and about 30% showing some improvement with intermittent relapses. A diagnosis of schizophrenia, therefore, has little predictive validity –
some people never pay to recover from the disorder, but many people do.

Question 20

A03: Reliability: A comment on cultural differences in the diagnosis of schizophrenia

Answer 20

Research (Barnes,2004) established cultural, and particularly racial, differences in the diagnosis of schizophrenia. However, the prognosis for members of ethnic minority groups may actually be more positive than for majority group members. The ethnic culture hypothesis predicts that ethnic minority groups experience less distress associated with mental disorders because of the protective characteristics and social structures that exist in most ethnic minority cultures. Brekke and Barrio (1997) and evidence to support this hypothesis in a study of 184 individuals diagnosed with schizophrenia or schizophrenia spectrum disorder. The sample was drawn from two non-white minority groups and a majority group. They found that non-minority group members were consistently more symptomatic than members of the two ethnic minority groups, findings which supported the ethnic culture hypothesis.

Question 21

A03: Reliability: Lack of inter-rater reliability

Answer 21

Despite the claims for increased reliability in DSM–111, over 30 years later there is still little evidence that DSM is routinely used with high reliability by mental health clinicians. Whaley (2001) found inter-rater reliability correlations in the diagnosis of schizophrenia as low as 0.11. Further problems with the inter-rater reliability of the diagnosis of schizophrenia are illustrated in the Rosenhan study.

Question 22

A03: Reliability: Unreliable symptoms

Answer 22

For a diagnosis of schizophrenia, only one of the characteristic symptoms is required if delusions are bizarre. However, this creates problems for the reliability of the diagnosis. When 50 senior psychiatrists in the US were asked to differentiate between bizarre numbers or delusions, they produce inter-rater reliability correlations of only around 0.40, forcing the researchers to conclude that even this central diagnostic requirement lacks sufficient reliability for it to be a reliable method of distinguishing between schizophrenic non-schizophrenic patients.