Validity refers to the extent that a diagnosis represents something that is real and distinct from other disorders and whether the ICD or DSM measure what they claim to measure.
What is the research into validity of diagnosing SZ
Cheniaux et al. (2009) found that when two psychiatrists assessed the same clients, using both ICD and DSM, that 68 were diagnosed with the ICD and only 39 under the DSM.
Inter-rater reliability refers to the extent that two clinicians will reach the same diagnosis. Test-retest reliability is whether the same diagnosis is reached for the same individual on two occasions by one clinician. Historically, reliability for diagnosis of Schizophrenia has been low but recent studies suggest higher reliability.
What is the research into reliability for diagnosing SZ
Osario et al. (2019) found inter-rater reliability of +.97 and +.92 for test-retest reliability in diagnosis of Schizophrenia.
However, some would state that of reliability is still an issue in diagnosis. Whaley found that when using the DSM-IV, inter-rater reliability correlations were as low as 0.11. Also, Beck et al (1961) found that agreement on diagnosis for 153 patients (where each was assessed by two psychiatrists from a group of four) was only 54%. Therefore, the current classification systems used to diagnose schizophrenia must lack inter-reliability.
Elaborate on rosenhans study as research support for reliability in diagnosing SZ
Further supporting the idea that there are significant issues with the classification symptoms is Rosenhan's study. In his study 'Being sane in insane places', all 8 'patient's were diagnosed with mental health issues and admitted to the psychiatric wards, despite them faking their initial symptoms. This study highlighted the unreliability of the diagnostic systems being used at the time. However, this study did take place over 40 years ago and diagnostic manuals have since been updated. For example, categories and definitions are more detailed and operationalised and psychiatrists now use standardised interview schedules when assessing patients. Also the ICD and DSM have been bought in line with one another so they are now very similar, so many of the studies discussed may now be outdated.
What are the issues in diagnosing SZ not including reliability and validity
Additionally, the patients may have co-morbid symptoms. This is the extent to which two (or more) conditions occur at the same time in a patient. Schizophrenia is often diagnosed alongside other conditions and this makes diagnosis and treatment difficult, and schizophrenia may not even be a distinct disorder. Finally, the classification systems may be culture and/or gender bias.
What research shows cultural bias in diagnosing SZ
Longnecker et al. (2010) found that more men than women have been diagnosed with Schizophrenia since the 1980s. Additionally, African-Caribbean British people are 9 times more likely to be diagnosed that White British people.
Reliability of diagnosis across cultures is also an issue for instance, Coupeland found that 69% of the US psychiatrists diagnosed Schizophrenia in patients but only 2% of British psychiatrists gave the same diagnosis for the same patients.
Cotton et al. (2009) found that more men are diagnosed with schizophrenia than women. However, this could be because women have more social support and so can function better in society. Therefore, the implication of this is that this can lead to an underdiagnosis and a lack of treatment for women.
In support of the issues of validity in diagnosis and classification of schizophrenia other studies have found comorbid symptoms. Swets et al. (2014) conducted a meta-analysis and found that 12% of schizophrenic patients also fulfilled the diagnostic criteria for OCD. Additionally, Buckley et al (2009) found that co-morbidity with depression is approx. 50% for those diagnosed with schizophrenia and a 47% co-morbidity with substance abuse.