Schizophrenia

Lesson Two

Specification

• Describe and evaluate two issues in classifying or diagnosing schizophrenia…

- Reliability- Validity

Issues in Classification and Diagnosis

What might these be?

Learning Objectives

• To define what is meant by the terms ‘reliability’ and ‘validity’

• To discuss how these effect the diagnosis of schizophrenia

• To be able to assess the reliability and validity of diagnosing schizophrenia using research evidence

Reliability

• How can we define reliability?

• Test Retest Reliability =

• Inter-rater reliability =

AO2/3 Marks

• We have lots of information/key words/descriptive knowledge

• How are we going to get the AO2/3 marks?

Research!!!

Inter-rater reliability – do psychiatrists agree?

• Beck et al (1961) looked at the inter-rater reliability between 2 psychiatrists when considering the cases of 154 patients.

• The reliability was only 54% - meaning they only agreed on a diagnoses for 54% of the 154 patients!

I wonder what the other bloke thinks?

• Söderberg (2005)• Reported a

concordance rate of 81% using the DSM-IV

• What does this suggest?

Inter-rater reliability – do psychiatrists agree?

I really hope I agree with that other bloke!

Inter-rater reliability – do psychiatrists agree?

• There is lots more research based evidence in your textbooks (p. 320-321)

• Summarise these findings in a paragraph

• In general what does the evidence suggest?

Validity

• How can we define validity?

• How can we assess validity?

Testing Validity• Reliability – a valid diagnosis has first to be reliable, does this guarantee validity?

• Predictive Validity – if diagnosis leads to successful treatment, the diagnosis is seen as valid, why is this difficult to attain?

• Descriptive Validity – to be valid, patients diagnosed with different disorders should differ from each other, why would this be reduced by comorbidity? Example?

• Aetiological Validity – to be valid, all patients with the same disorder should have the same cause, is it this simple?

On Being Sane in Insane Places• Rosenhan (1973) recruited 8 people • Each of the 8 people went to a psychiatric hospital

and reported only 1 symptom. That a voice said only single words, like “thud”, “empty” or “hollow”.

• When admitted, they began to act “normally”.• All were diagnosed with suffering from

schizophrenia (apart from 1). • The individuals stayed in the institutions for between

7 to 52 days.

On being sane… follow up• Rosenhan told the institutions about his results, and

warned the hospital that they could expect other individuals to try & get themselves admitted.

• 41 patients were suspected of being fakes, and 19 of these individuals had been diagnosed by 2 members of staff.

• In fact, Rosenhan sent no-one at all!

Rosenhan (1973)

• What does this study mean in terms of validity of diagnosis?

• What does this study tell us about the effect of “labelling”

• BUT… what issues are there with the study?

Cultural Relativism

• Classification systems reflect WESTERN culture – why might this be a problem?

Homework: Due Monday 15th Sept.

• Using the hand-out / textbook / internet research / books in the library etc.Answer the questions:

1. Comment on the differences between the ICD-10 and DSM-IV classification systems and the consequences of this for reliability

2. Explain how reliability may be affected by using different criteria for diagnosis

3. Comment on the differential number of sub-types in DSM-IV and ICD-10 – how does this affect reliability?

Final Check

• What is Reliability?• What is Validity?• How can we test reliability?• How can we test Validity?