Diagnosis and classification of schizophrenia

• No single defining characteristic: collection of seemingly unrelated symptoms, many misconceptions+exagerations surrouding the nature of schizophrenia.
• DSM-5 and ICD-10 differ: 
• DSM 5: one + symptom must be present (delusions, hallucinations).
• ICD-10: two or more - symptoms=sufficient for diagnosis (avolition, speech poverty).
• Symptoms:
• + symptoms= additional experiences beyond those that already exist:
• Hallucinations: sensory experiences that have distorted perceptions of real things, e.g. seeing people who aren't there.
• Delusions: Beliefs that no basis in reality- person with schizophrenia behaves in a way that is normal to them, but bizzare to others, e.g. being victim of a conspiracy.
• - symptoms= loss of usual abilities+experiences
• Avolition: severe loss of motivation to carry out everyday tasks (work, personal hygiene), unwillingness to carry out goal-directed behaviour.
• Speech poverty: reduction in amount+quality of speech- delay in verbal responses during conversation.

Key issues:

• Reliability: extent to which the diagnosis of schizophrenia is constistant.
• Validity: extent to which diagnosis+classification techniques measure what they are designed to measure.
• Co-morbidity: occurence of two illnesses together which confuse diagnosis+treatment.
• Symptom overlap: when two or more conditions share symptoms, questioning validity of the classification.

• Diagnosis of schizophrenia has low reliability:
• Cheniaux et al. (2009) had two psychiatrists diagnose 100 pp's using DSM and ICD criteria.
• Inter-rater reliability was poor; one psychiatrist diagnosed 70 with schizophrenia using both criteria, the other diagnosed 37.
• Inconsistency between mental health professionals and different classification systems is a limitation of the diagnosis because it supports the theory that the consistency of  the diagnosis of schizophrenia is low.

• Diagnosis of schizophrenia has low validity:
• Standard way to assess validity of diagnosis is criterion validity, do different assessment systems meet the same criteria, thus arriving at the same diagnosis?
• Cheniaux et al.'s study shows that schizophrenia is much more likely to be diagnosed using ICD than DSM.
• Suggest that schizophrenia is either over-diagnosed in ICD or under-diagnosed in DSM, which highlights the low validity of the diagnosis.

• Gender bias in the diagnosis of schizophrenia:
• Longenecker et al. (2010) reviewed studies that showed that since the 1980s men have been diagnosed more often than women.
• Cotten et al. (2009) found female patients function better than men. Could explain why some women escape diagnosis because their stronger interpersonal functioning may bias practioners to under-diagnose schizophrenia.
• Problem because men and women with similar symptoms may experience differing diagnoses. Consequently, gender bias decreases the reliability of the diagnosis because men are being over-diagnosed and women are being under diagnosed.

• Cultural bias in the diagnosis of schizophrenia:
• African-Americans are much more likely to be diagnosed with the illness in the UK. Whereas, rates of diagnosis are much lower in the West Indies and Africa.
• Higher diagnosis rates in the UK could be due to some behaviour that is classed as a postive symptom is normal in African cultures, e.g. hearing voices as part of ancestor communication.
• Highlights the issue of validity of diagnosis because it suggests that individuals from some cultural backgrounds are more likely to be diagnosed than others to cultural bias.