diagnosis and classification

• classification of schizophrenia 


  the two major systems for the classification of mental disorder are ICD-10 and the DSM-5. these differ slightly in their classification. e.g. in the DSM-5 system one of the positive symptoms such as delusions, hallucinations or speech disorganisation must be present for diagnosis whereas two or more negative symptoms are sufficient under ICD
• positive symptoms

  hallucinations = these are unusual sensory experiences. some hallucinations are related to events in the environment where as some have no relationship to what the senses are picking up from the environment. hallucinations can be experienced in relation to any sense. e.g. a person may see distorted facial expressions or people that aren't there
• positive symptoms

  delusions = they are irrational beliefs. common delusions involve being an important historical, political or religious figure such as Jesus and also commonly involves being persecuted. another class of delusions concerns the body. people with delusions may believe that part of them is under external control. delusions can make people behave in a way that is bizarre to others. some delusions can lead to aggression
• negative symptoms

  avolition = finding it difficult to begin or keep up with goal-directed activities. people with schz often have reduced motivation to carry out a range of activities. Andreason identified 3 identifying signs of avolition: poor hygiene, lack of persistence in work and lack of energy
• negative symptoms

  speech poverty = the ICD-10 recognises speech poverty as a negative symptom. this is because the emphasis is on reduction in the amount and quality of speech in schizophrenia. this is sometimes accompanied by a delay in the person's verbal responses during conversations.
• inter-rater reliability 


  the extent to which different assessors agree on their assessments. in diagnosis this means the extent to which two or more health professionals arrive at the same diagnosis for the same individual.
• A03- reliability

  • Cheneaux et al had two psychiatrists independently diagnose 100 people using both DSM and ICD criteria
  • inter-rater reliability was poor, with one psychiatrist diagnosing 26 with schizophrenia according to DSM and 44 to ICD
  • the other diagnosing 13 according to DSM and 24 to ICD, making it a weakness for diagnosis
• criterion validity

  do different assessment systems arrive at the same diagnosis for the same person
• A03- validity

  • Cheneaux 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, showing the validity is poor
• co-morbidity 


  the phenomenon that two or more conditions that occur together. if conditions occur together a lot of the time this questions the validity. of their diagnosis and classification because they might actually be a single condition
• A03 - co-morbidity

  • Buckley et al concluded around half of people with schizophrenia also have a diagnosis of depression (50%) or substance abuse (47%)
  • PTSD also occurred in 29% of cases and OCD in 23%
  • it is a confusing picture whether the conditions are similar or not making it a weakness of the diagnosis and classification
• symptom overlap

  • both schizophrenia and bipolar disorder include positive symptoms like delusions and negative symptoms like avolition
  • under ICD a person may be diagnosed with schizophrenia however the same individual could be diagnosed with bipolar disorder under DSM