diagnosis and classification of schizophrenia

• Schizophrenia is a severe mental disorder where reality and insight are impaired. It is experienced by 1% of the worlds population and most commonly diagnosed in men, city-dwellers and low socio-economic groups.
• A positive symptom of schizophrenia is hallucinations. Experiencing hallucinations means perceiving things around us that aren’t real. Hallucinations can involve any of the five senses.
• A positive symptom of schizophrenia is delusions. Delusions are irrational beliefs about the world, that are firmly held onto.
• A negative symptom of schizophrenia is avolition. Avolition is a persistent lack of motivation or energy to complete normal, everyday tasks.
• A negative symptom of schizophrenia is speech poverty. Speech poverty is minimal speech and a lack of spontaneous, unprompted speech.
• Positive symptoms are symptoms that involve abnormal, additional experiences that people don’t normally have.
• Negative symptoms are symptoms that involve absence of experiences that people normally have.
• Schizophrenia is diagnosed using the Diagnostic Statistical Manual. To be diagnosed with schizophrenia, patients must display at least 2 of the main symptoms for at least 6 months.
• A reliable diagnosis is when different doctors give the same diagnosis consistently to one patient whose symptoms remain the same or when one doctor gives different patients with the same symptoms the same diagnosis consistently.
• A diagnosis is valid when the criteria used to make the diagnosis allow us to correctly identify people who have a particular illness and doctors don’t incorrectly diagnose people who don't have a particular illness.
• Diagnosis for schizophrenia has good reliability. Inter-rater reliability has been used to assess the reliability of schizophrenia diagnosis and in 2005, researchers found that they were 81% similar. This is positive as we can be reasonably sure the diagnosis of schizophrenia is consistently applied.
• Low validity for schizophrenia diagnosis. Rosenhan conducted an observational study using 8 volunteers who pretended to have schizophrenia and be admitted into hospital. Rosenhan found that it took doctors between 7 and 52 days to realise the diagnoses were wrong, and that the volunteers were healthy. This is problematic as it shows that the diagnosis of schizophrenia can lack validity.
• Culture bias. Social norms vary between cultures. For example, hallucinations are seen to be normal in some cultures, such as Haiti, but in the UK it would indicate schizophrenia. Pinto and Jones 2008 found those of Afro-Caribbean origin are 9x more likely to receive a diagnosis than white British people. This is problematic as doctors might be more likely to diagnose someone from another culture with a mental disorder, reducing the reliability and validity of the diagnosis.
• gender bias. Men are more commonly diagnosed with schizophrenia than women. Loring and Powell 1988 gave male and female doctors identical descriptions of a patient’s symptoms but varied the patient's gender. 20% of doctors diagnosed female patients with schizophrenia, but 56% diagnosed the man with schizophrenia. This is problematic as it indicates there may be alpha bias in the diagnosis of schizophrenia.
• Co-morbidity with other conditions. Buckley et al 2009 investigated how many schizophrenic patients had a comorbid mental disorder and found 50% of patients had depression and schizophrenia, 47% of patients had an addiction and schizophrenia, and 23% of patients had OCD and schizophrenia. This is problematic as schizophrenia may not be a distinct condition and diagnostic criteria may lack validity.