Discuss issues of reliability and validity in classification and diagnosis of schizophrenia (24 marks).
Clinical researchers prefer schizophrenia categorised into two types. Positive symptoms known as behavioural excess which show a number of symptoms such as: delusions, hallucinations and distorted thinking. Schizophrenics that show positive symptoms are less likely to show brain abnormalities and are easily more effective to be treated by medicine. Negative symptoms are known as behaviour deficits and include the following: lack of emotional expression, Â lack of interest, lack of interest in the world and speech difficulties. Those with negative symptoms of schizophrenia are more likely to show structural brain abnormalities and medicine treatments are less likely to be as effective as on positive symptoms.
Validity is the extent to which the person who is diagnosed with schizophrenia actually has the disorder. For the diagnosis to be valid it must also have high reliability. For example if psychiatrists cannot agree who has schizophrenia (low reliability) then questions of what it is become essentially meaningless. Reliability is the extent to which psychiatrist can agree on the same diagnosis when independently assessing patients (inter-rater reliability). Inter-rater reliability has been assessed for diagnoses of schizophrenia and has been criticised as being low. Though Carson claimed that DSM-III gave psychiatrists a reliable classification system with greater agreement on who had schizophrenia, this isn’t necessarily true and later revisions have continued to produce low inter-rater reliability scores. For example, Whaley found only a small positive correlation of +0.11 between different raters. Thomas Szasz argues that the DSM and ICD lack reliability and validity. Szasz suggest that mental illness is a myth created by psychologist and psychiatrist for economic reasons and social control. Szasz also argues the DSM lacks scientific validity as it is not based on credible evidence. Therefore it is subject to the psychologists opinion and there are case study examples of misdiagnosis and inconsistencies to support Szaszs claim.
A study by Rosenhan demonstrates how clinicians can wrongly diagnose schizophrenia. eleven out of twelve hospitals diagnosed schizophrenia to the psuedopatients  and were released as schizophrenics in remission and had an average length of stay in the facility for 19 days (longest 52 days) despite the pseudopatients behaving normally. This clearly demonstrates poor validity of diagnosis of schizophrenia as none of patients had schizophrenia. However the findings show good reliability as 11/12 different psychologist diagnosed the psuedopatients with schizophrenia after hearing the same symptoms. Rosenhan did a follow up study where they told staff to expect one or more psuedopatients over 3 months. 193 patients had been admitted and staff were asked the likelihood of the patient being ‘real’ when all the patients were actually real. They reported that 20% were psuedopatients and 10% fake therefore 83/193 were suspected as pseudopatients. This suggest that medical staff cannot tell the difference between mental illness and normal behaviour. These findings clearly demonstrate that there is poor validity and reliability diagnosis of schizophrenia and the expectations of psychiatrists can influence the bias for there diagnosis. However critics have argued that
Cultural bias is the extent to which the diagnostic system reflects beliefs about what is viewed as normal and acceptable in western, predominantly white which reduces the validity. A lack of cultural relativism means other cultures may view hearing voices as normal or desirable but in western culture is mainly viewed as a symptom of schizophrenia by the DSM and ICD which are therefore argued to lack cultural validity. The Health Development Agency have found that young black men are over-represented in the mental health statistics (Nazroo) as schizophrenia has been reported to be three times higher in black caribbean population than the white population in the UK. It was also found by Fernanda et al they are also more likely to be admitted to mental health facilities as compulsory and more likely to be placed in locked wards. These findings show that the DSM lacks cultural validity and are culturally biased which causes the DSM to lack validity as some of the individuals from other cultures may not have schizophrenia. Alternatively it is argued that ethnic minorities in the UK are more likely to be diagnosed with schizophrenia because they live more stressful lives due to social factors such as racism. Thus triggering the schizophrenia that otherwise would have laid dormant. Therefore, the difference would be due to social and environmental factors not a biased diagnosis.
Copeland sent patient descriptions to the US and UK and found 62% of US psychiatrists diagnosed schizophrenia to the patient however in the UK 2% of psychiatrists only diagnosed schizophrenia. These findings show a lack of reliability as if the patient did have the symptoms of schizophrenia all psychiatrist should have diagnosed the patient with schizophrenia. However the results may have been different with when the study is replicated with up to date diagnostic systems.
As there is no biological test for schizophrenia it is impossible to generate a perfect diagnostic system and as a result diagnosis of schizophrenia relies on the subjective interpretation of the psychiatrist. The diagnosis may be influenced unintentionally by the psychiatrists own expectations or prejudices which leads to issues of validity and reliability within the classification and diagnosis of schizophrenia. The DSM-V aims to address the issue of low validity by improving the validity of the diagnostic systems.
