Diagnosis and classification of schizophrenia

• There is no single characteristic of schizophrenia
• Schizophrenia is a collection of seemingly unrelated symptoms. There are many misconceptions and exaggerations surrounding the nature of schizophrenia
• What are the two types of symptoms of schizophrenia?

  Positive and negative
• Positive symptoms:

  additional experiences beyond those of ordinary experiences
• Negative symptoms:

  loss of usual abilities and experiences
• Two examples of positive symptoms:

  Hallucinations and delusions
• Two types of negative symptoms:

  Avolition and speech poverty
• Hallucinations:

  Sensory experiences that have no basis in reality or distorted perceptions of real things. Experienced in relation to any sense.

  For example, hearing voices or seeing people who aren't there
• Delusions:

  Beliefs that have no basis in reality- make a person with schizophrenia behave in ways that make sense to them but are bizarre to others

  For example, beliefs about being a very important person or the victim of a conspiracy
• Avolition:

  Severe loss of motivation to carry out everyday tasks (e.g. work, hobbies, personal care)

  Results in lowered activity levels and unwillingness to carry our goal-directed behaviours
• Speech poverty:

  A reduction in the amount and quality of speech. May include a delay in verbal responses during conversation

  DSM emphasises speech disorganisation and incoherence
• Four key issues:

  1. Reliability: extent to which the diagnosis of schizophrenia is consistent
  2. Validity: extent to which the diagnosis and classification techniques measure what they are designed to measure, in this case to measure schizophrenia
  3. Co-morbidity: occurrence of two illnesses together which confuses diagnosis and treatment
  4. Symptom overlap: when two or more conditions share symptoms, questioning the validity of the classification
• Four main issues in diagnosis of schizophrenia:

  Reliability, validity, co-morbidity and symptom overlap
• Limitation: diagnosis is low reliability

  Cheniaux et al. had two psychiatrists independently diagnose 100 patients using both DSM and ICD criteria. Inter-rater reliability was poor. One psychiatrist diagnosed 26 with schizophrenia using DSM and 44 using ICD. Second psychiatrist diagnosed 13 with DSM and 24 with ICD. This inconsistency between mental health professionals and the different classification systems is a limitation of diagnosis
• Limitation of diagnosis: validity

  A standard way to assess validity of a diagnosis is criterion validity- do different assessment systems arrive at the same diagnosis for the same patient? Cheniaux et al.'s study shows that schizophrenia is much more likely to be diagnosed using ICD than DSM. This suggests that schizophrenia is either over-diagnosed in ICD or under-diagnosed in DSM. This is poor validity and a weakness of the diagnosis
• Limitation of diagnosis: co-morbidity

  Co-morbidity is when two or more conditions occur together. If conditions occur together a lot of the time it might call into question whether they are actually a single condition. Buckley et al. concluded that around half of patients with a diagnosis of schizophrenia also have a diagnosis of depression (50%) or substance abuse (47%). In terms of classification, if very severe depression looks like schizophrenia and vice versa, it may be that they are a single condition. This confusing picture is a limitation
• Limitation: cultural bias

  African-Americans and English people of African origin are much more likely to be diagnosed with schizophrenia in the UK. Rates in the West Indies and Africa are not high, so this is not a genetic vulnerability. High diagnosis rates in the UK may be because some behaviours classed as positive symptoms of schizophrenia are normal in African cultures (e.g. hearing voices in ancestor communication). This highlights an issue in validity of diagnosis because it suggests that people from some cultural backgrounds are more likely to be diagnosed than others due to bias.