Reliability and Validity of Classification and Diagnosis

• There may be poor inter-rater reliability in the classification and diagnosis of schizophrenia. For example, Cheniaux et al (2009) had two psychiatrists independently diagnose 100 (already schizophrenic) patients using both the DSM and the ICD criteria. They found that the first psychiatrist gave more diagnoses regardless of the classification system. This shows that clinicians are not consistent in using the classification systems to diagnose people, meaning that it is unreliable.  
• There may be poor criterion validity in the classification and diagnosis of schizophrenia. For example, Cheniaux et al (2009) had two psychiatrists independently diagnose 100 (already schizophrenic) patients using both the DSM and the ICD criteria. They found that the ICD led to more schizophrenia diagnoses than the DSM by both psychiatrists. This suggests clinicians using the ICD are likely to over diagnose patients with schizophrenia, while those using the DSM are likely to under diagnose patients with schizophrenia, showing that neither classification may be accurate.  
• The validity of schizophrenia classification and diagnosis may be brought into question by the possibility of co-morbidity. For example, schizophrenia and bipolar disorder occurring together. If conditions occur together a lot of the time, then this questions the validity of their diagnosis and classification as they might actually be one single condition, rather than two separate ones.  
• The classification of schizophrenia's validity may be brought into question by symptom overlap. For example, both schizophrenia and bipolar disorder involve delusions and avolition. Using the ICD, a patient may be diagnosed as schizophrenic but may be diagnosed as bipolar using the DSM. This lessens the validity as it suggests different classification systems may give different outcomes, meaning people may be diagnosed with the wrong mental illness and may not be getting appropriate treatment.  
• The reliability of schizophrenia classification and diagnosis is brought into question by the presence of culture bias
• In Britain, Afro-Caribbeans are more likely than white people to be diagnosed with schizophrenia
• This cannot be due to differences in genetic vulnerability as rates of schizophrenia are not higher in Africa and the West Indies
• Hearing voices is more acceptable in African cultures due to cultural beliefs
• The reliability of schizophrenia diagnosis is also questionable due to the presence of gender bias
• Gender bias in schizophrenia diagnosis


  Since the 1980's men have been diagnosed with schizophrenia more than women
• If hearing voices is reported to a clinician with a different cultural background


  It can be seen as bizarre and irrational
• Males


  • More genetically vulnerable to schizophrenia
• Diagnosis and classification is different depending on the cultural background of the patient
• Female patients


  • Tend to function better than men (e.g. more likely to work and have better interpersonal skills)
• Female patients' high functioning


  May have prevented a schizophrenia diagnosis as clinicians have misapplied the diagnostic criteria
• When men with similar symptoms might have been diagnosed, clinicians may be misapplying the classification system based on gender
• This means schizophrenia classification and diagnosis may not be reliable