Diagnosis and classification

• what are the systems for the classification of mental disorder?

  • World Health Organisation's International Classification of disease
  • ICD-10
  • American Psychiatric Association's Diagnostic and Statistical Manual edition 5 (DSM-5)
• Positive symptoms

  • atypical symptoms experienced in addition to normal experiences.
  • includes hallucinations and delusions
• hallucinations

  unusual sensory experiences that either have no basis in reality or are distorted perceptions of things that are there
• delusions

  involves beliefs that have no basis in reality
• negative symptoms

  • atypical experiences that represent the loss of a usual experience
  • includes speech poverty and avolition
• speech poverty

  reduced frequency and quality of speech
• avolition

  loss of motivation to carry out tasks and results in lowered activity levels
• strength of diagnosis - reliability

  • a psychiatric diagnosis is reliable when different diagnosing clinicians reach the same diagnosis for the same individual (inter-rater reliability) and when the same clinician reaches the same diagnosis for the same individual on two occasions (test-retest reliability)
  • Osorio et al
  • reported excellent reliability for the diagnosis of SZ in 180 individuals using the DSM-5
• limitation of diagnosis - validity

  • Cheniaux et al
  • 2 Psychiatrists independently assessed the same 100 clients using ICD-10 and DSM-iv criteria.
  • found 68 diagnosed under ICD and 39 under DSM.
  • suggests SZ may be over or under diagnosed according to the system.
  • low criterion validity
• limitation of diagnosis - co-morbidity

  • SZ is commonly diagnosed with other conditions.
  • E.g. a review found half of those diagnosed with SZ also had a diagnosis of depression or substance abuse.
  • Means SZ may not exist as a distinct condition
• limitation of diagnosis - gender bias

  • men have been diagnosed with SZ more commonly than women - ratio of 1:4:1
  • likely that women are underdiagnosed because they have closer relationships and get support.
  • leads to women with SZ functioning better than men.
  • means women may not be receiving treatment that could benefit them
• limitation of diagnosis - culture bias

  • symptoms of SZ have different meanings in different cultures
  • e.g. in Haiti some people believe that hearing voices are communications from ancestors.
  • British African-Caribbean people may be discriminated against due to a culturally-biased diagnostic system.
• limitation of diagnosis - symptom overlap

  • there is considerable overlap in symptoms of SZ and other disorders.
  • Both SZ and bipolar disorder involve positive symptoms of delusions and negative symptoms of avolition.
  • this suggests SZ and bipolar may not be different conditions but variations of the same condition in terms of classification.
  • in diagnosis, SZ is hard to distinguish from bipolar disorder.