Diagnosis and classification of schizophrenia

• What is schizophrenia?

  A severe mental disorder where contact with reality and insight are impaired.
• The two major systems for the classification of mental disorder are ICD-10 and DSM-5.
• The two systems differ in their classification of schizophrenia. For example, in DSM-5 one positive symptom must be present for diagnosis whereas two or more negative symptoms are sufficient under ICD.
• ICD-10 recognises a range of subtypes of schizophrenia, such as paranoid schizophrenia and catatonic schizophrenia.
• What are the two positive symptoms of schizophrenia?

  Hallucinations and delusions.
• What are the two negative symptoms of schizophrenia?

  Avolition and speech poverty.
• What are hallucinations?

  A positive symptom of schizophrenia. They are sensory experiences of stimuli that have either no basis in reality or are distorted perceptions of things that are there.
• What are delusions?

  A positive symptom of schizophrenia. They involve beliefs that have no basis in reality, for example, that the person with schizophrenia is someone else.
• What is avolition?

  A negative symptom of schizophrenia. It involves loss of motivation to carry out tasks and results in lowered activity levels.
• What is speech poverty?

  A negative symptom of schizophrenia. It involves reduced frequency and quality of speech.
• AO3 - Reliability:

  Cheniaux et al. (2009) had two psychiatrists independently diagnose 100 people using both DSM and ICD criteria. Inter-rater reliability was poor, with one psychiatrist diagnosing 26 with scz according to DSM and 44 according to ICD, and the other diagnosing 13 according to DSM and 24 according to ICD. This poor reliability is a weekness of diagnosis of schizophrenia.
• AO3 - Validity:

  In the Cheniaux et al. study, we can see that scz is much more likely to be diagnosed using ICD than DSM. This suggests that scz is either over-diagnosed in ICD or under-diagnosed in DSM. This is poor validity.
• What is co-morbidity?

  The occurrence of two disorders or conditions together, for example a person has both schizophrenia and a personality disorder.
• What is symptom overlap?

  Occurs when two or more conditions share symptoms.
• AO3 - Co-morbidity:

  Buckley et al. (2009) concluded that around half of people with a diagnosis of scz also have a diagnosis of depression. In diagnosis, this could suggest we are bad at telling the difference between the two conditions. In terms of classification, if depression looks a lot like scz and vice versa, then they might be better seen as a single condition. This confusion is a weakness of diagnosis and classification.
• AO3 - Symptom overlap:

  Both scz and bipolar disorder involve positive symptoms and negative symptoms. Under ICD a person might be diagnosed with scz; however, many of the same individuals would receive a diagnosis of bipolar disorder according to DSM criteria. This call into question the validity of both the classification and diagnosis of schizophrenia.
• AO3 - Cultural bias in diagnosis:

  African Americans and people of Afro-Caribbean origin are several times more likely than white people to be diagnosed with scz. Positive symptoms such as hearing voices may be more acceptable in African cultures because of cultural beliefs in communication with ancestors. When reported to a psychiatrist from a different cultural tradition these experiences are likely to be seen as irrational.