There are 2 main diagnostic systems used
- Reliability of schizophrenia (sz) is difficult to attain because psychiatrists in different countries use different classifications systems. These systems have an emphasis on different systems. For example, the DSM, which is used in the USA, has 5 sub-types of sz and symptoms need to be there for 6 months before diagnosis. The ICD-10, used in Europe, has 7 sub-types (it includes post-sz depression and simple sz too) and symptoms need to be there for 1 month before diagnosis. This means that people can get different diagnoses in different countries, reducing the reliability.
- This can be seen from Copeland et al who gave a description of a patient to both US and UK psychiatrists. 69% of US psychiatrists diagnosed sz compared to only 2% of UK. This signifies how sz has low inter-rater reliability.
- Therefore, this suggests that as clinicians are unable to agree on sz, people with different syptoms (different types of behaviours) may get the same diagnosis, lowering the reliability of the disorder.
Sz diagnosis has changed over time
- Furthermore, common use of the term 'sz' has mean that diagnostic rates have changed over time. For example, research has found that in the 1920s in the USA, 20% of those suspected were diagnosed with sz. This number rose to 80% in the 1950s. But, in the UK, the number has stayed around 20%. This implies that people diagnosed in the past may not be diagnosed in the same way today and may have received inappropriate treatment.
- This suggests that the diagnostic systems used are not reliable over time. In order to get rid of these diagnostic differences, the systems have been brought more in line with each other and criteria given narrower terms.
- Therefore, even though this has happened, there are still major differences in diagnostic rates between the systems, showing there is low reliabilty of diagnosis.
Diagnosis relies on the skill of the clinician
- Additionally, diagnosis relies on the skill of the clinician which makes it even less reliable. This high reliance is not seen in other areas of medicine, for…