Reliability and validity in diagnosis and classification Flashcards
Define reliability.
The consistency of measurements across time, conditions and researchers.
Define validity.
Refers to whether an observed effect is a genuine one. If it is based on truth, fact, accuracy or law.
What does reliability refer to in terms of SZ diagnosis?
Diagnosis of SZ is repeatable over time and between clinicians.
Who investigated cultural differences in the diagnosis of SZ?
Copeland.
How did Copeland investigate cultural differences in diagnosis of SZ.
134 US and 194 British psychologists. Given description of SZ patient, asked whether they would issue a diagnosis.
What did Copeland find in his study?
69% US psychologists diagnosed SZ, 2% British psychologists.
What are the three validity issues in SZ diagnosis?
Gender bias
Symptom overlap
Co-morbidity
How is SZ diagnosis gender biased?
US clinicians found to equate healthy adult behaviour with healthy male behaviour. Pathologises females, as women are perceived as less mentally healthy.
Describe how symptom overlap affects validity of the diagnosis of SZ.
Many SZ symptoms also found in other disorders. E.g. delusions in depression. People with dissociative identity disorder have more SZ symptoms than SZ patients. Makes SZ more difficult to accurately diagnose - validity.
Describe how co-morbidity affects validity of diagnosis of SZ.
When two or more conditions/diseases occur simultaneously in a patient. Estimated co-morbid depression occurs in 50% of SZ patients. Complicates diagnosis process. Suggests separate disorders not as clear-cut as assumed.
(AO3) Describe research support for gender bias in SZ diagnosis.
Loring and Powell random sample 290 male and female psychiatrists. Read two case descriptions of patients’ behaviour. Asked to offer diagnosis using standard diagnostic criteria. Described as male or no gender info = 56% diagnosis. Described as female = 20% diagnosis. This bias was not as evident among female psychiatrists.
(AO3) What further evidence (not research) is there for the low validity of SZ classification?
Differences in prognosis (course of a condition and its outcomes). For recovered patients: 10% improved function, 20% recover previous level of functioning, 30% recover functioning with relapses. Little predictive validity.
(AO3) What evidence is there for the low reliability of SZ diagnosis?
Lack of inter-rater reliability. Some clinicians argue it is better than 30 years ago. But inter-rater reliability found to be as low as 0.11. Extremely bad. Evidence for bla bla bla.
(AO3) Explain research into cultural differences in SZ.
Comparison of USA, China and Taiwan. Basic symptoms of SZ were similar. Experience and interpretation of symptoms very different. USA = biological disease. China, Taiwan = social/moral problem requiring family and community support. Lower rates of SZ in China due to closely-knit social networks in rural Chinese communities. Challenges the universality of SZ and importance of cultural factors.
