A01: Reliability - Differences between Clinicians
Klietman suggested several issues that affects reliablilty. One of which is Differences in Clinicians. Clinicians may interpret symptoms differently e.g. 'bizarre' hallucinations.
Mojtabi and Nicholson asked 50 psychiatrists to seperate and label bizzare and non-bizzare hallucinations. A low concordance rate (Correllation) of 0.4 was found. Therefore showing that diagnosis of schizophrenia can lack reliabilty.
A01: Reliability - Differences between Patients
- Symptoms that the patient displays on the day of their interview can affect the diagnosis
- Patients with an ethinic background affect the diagnosus as Clincians are six times more likely to diagnose schizophrenia if the patient is black (usually if diagnosed by white male)
A01: Reliability - Differences in Procedures
- The DSM was produced in America by the American Psychiatric Association
- The ICD was developed in Europe by the World health organisation
- In the UK diagnosis is usually carried out using the DSM
Suggesting that there are no true objective diagnosis tests for schizophrenia
A02: Reliabilty - Support
Beck et al: They reported a 54% concordance rate between experienced practitioners diagnosis when assessing 153 patients. This shows that there is consistancy between doctors, suggesting reliabilty of diagnosis.
Jakobsen et al: found a concordance rate of 98% in diagnosing 100 Danish Patients suggesting there is a consistancy when diagnosing schizophrenia, making the diagnosis reliable.
A02: Reliabilty - Critisism
Read et al: reported a test-retest with the reliabilty of diagnosis to have only a 37% concordance rate showing that there was no consistancy over time when diagnosing schizophrenia and suggesting low reliabilty.
Copeland's: raises cultural issues. They gave descriptions of patients to 134 US and 194 British psychiatrists. 69% US psychiatrists diagnosed schizophrenia whilst only 2% of the British did. This shows there's no consistancy between clinicians diagnosing schizophrenia, and therefore there's low reliabilty.
A01: Validity - Predictive Validity
If something has predictive validity the classification system should be able to predict the outcome in response to treatment.
It's hard to predict this with accuracy. Heather argued there is only a 50% chance that clinicians can predict what treatments patients will recieve, which suggests dianosis is not valid.
There's no evidence that people who are diagnosed with Schizophrenia, share the same outcomes as only 20% recover to normal level of functioning, 10% show lasting improvement and about 30% showing some improvement with intermittent relapses and some never appear to recover from the disorder.
A01: Validity - Descriptive Validity + Comorbidity
Schizophrenia should be distinguished form other psychotic disorders.
Allardyce et al suggested that there are many combinations of symptoms that a patient could show to classify being schizophrenic. Therefore, schizophrenia must not be a seperate disorder and so diagnosis is invalid. There is a marked variabilty among those with Schizophrenia eg, symptoms, course and treatment. This questions whether schizophrenia is a single mental disorder at all.
Comordity: Where patients have two or more disorders simultaneously.
If symptoms of depression are present when diagnosing Schizophrenia, means a consequence of this depression is co-morbid with schizophrenia and therefore scizophrenia cannot be diagnosed accurately.
A02: Validity - Support
Hollis - studied 93 cases of early onset Schizophrenia, using the DSM to the patients case notes. The findings suggested that the diagnosis of schizophrenia has a high level of stability suggesting that diagnosis are to a large extent valid. Plus, careful diagnosis can lead to effective treatment programmes.
A02: Validity - Critisism
Bottas - suggested there are different types of schizophrenia. They reported the incidence of schizophrenia is 1% and about 3% for obsessive compulsive disorder. There is genetic and neurobiological evidence that suggests there's a separate schizo-obsessive disorder. Therefore accurately diagnosing schizophrenia may be very difficult, and so diagnosis may not be valid.
Scheff - suggested the 'sticky label' effect. It's difficut to remove and has serious consequences. This suggested that schizophrenics don't have periods of rational behaviour, when they actually do. The negative label is therefore stuck for life and describes the person rather than the disorder. A label that's misdiagnosed could lead to a self-fulfilling prophecy affecting the validity of the diagnosis.
A01/2: Cultural Differences affecting validity of
A01: The problem with using the ICD and the DSM is that in one culture it maybe seen as normal behaviour but as schizophrenic in another. In some cultures and religions hearing voices is regarded being healthy and a sign of spiritual development.
A02: Lu et al found that in many cultures 'seeing' or being visited by a recently deceased person isn't unusual among family members. Therefore the DSM and ICD are culturally biased.
A01: the cultural background of psychiatrists may lead to misinterpretation and misdiagnosis. For example if someone's social norms and behaviours are different to their own they may view normal emotional shyness as the flattening affect.
A02: Lawson et al found African American patients are more likely to be diagnosed with severe psychotic disorders in a clinical setting than white patients. This again raises concern over the issue in validity in testing of schizophrenia.