Diagnosis and classification of schizophrenia

• Diagnosis and classification of schizophrenia

  Schizophrenia is a severe mental disorder where contact w/ reality and insight are impaired, an example of psychosis.
• Diagnosis and classification of schizophrenia 2

  Classification

  Two major systems are (differ in classification):

  • ICD-10 - 2 or more negative symptoms. Recognises subtypes e.g., catatonic schizophrenia (disturbance to movement, leaving the person immobile or alternatively overactive).
  • DSM-5 - 1 positive symptom. Older editions recognised subtypes but was dropped in DSM-5.
• Diagnosis and classification of schizophrenia 3

  Positive symptoms

  Atypical symptoms experienced in addition to normal experiences.

  • Hallucinations - Unusual sensory experiences. Some related to events in the environment whereas others do not (E.g., voices heard talking to the person, often criticising them). Can be experienced in relation to any sense.
  • Delusions - Irrational beliefs (also known as paranoia). Common delusions involve being an important historical/religious/political figure or being persecuted by government/aliens or they are under external control.
• Diagnosis and classification of schizophrenia 4

  Negative symptoms

  Atypical experiences that represent the loss of a usual experience.

  • Avolition - Finding it difficult to begin or keep up w/ goal-orientated activity. Reduced motivation. Andreason (1982) identified three signs of avolition: poor hygiene and grooming, lack of persistence in work or education and lack of energy.
  • Speech poverty - Characterised by changes in patterns of speech. Reduction in amount and quality of speech, delayed response, changing topic mid sentence, etc.
• Diagnosis and classification of schizophrenia- evaluation

  Reliability means consistency. An important measure of reliability is inter-rater reliability, which in the case of diagnosis this means the extent to which two mental health professionals arrive at the same diagnosis for the same individuals. Cheniaux et al. (2009) had two psychiatrists independently diagnose 100 people using both DSM and ICD criteria. Inter-rater reliability was poor:

  • DSM- 26 , ICD- 44
  • DSM- 13, ICD- 24
• Diagnosis and classification of schizophrenia- evaluation 2

  Poor validity. The extent to which we are measuring what we are intending to measure. One standard way to assess validity of a diagnosis is criterion validity; do diff assessment systems arrive at the same diagnosis for the same person? Cheniaux et al. study shows sz is much more likely to be diagnosed using ICD than DSM. Is either over-diagnosed or under-diagnosed.
• Diagnosis and classification of schizophrenia- evaluation 3

  Co-morbidity is the phenomenon that 2 or more conditions occur together. Buckley et al. (2009) concluded 50% diagnosed w/ sz are diagnosed w/ depression or substance abuse (47%). Poses challenge to both classification and diagnosis of sz. In terms of classification, severe depression may look like sz and vice versa, might be better seen as a single condition. In terms of diagnosis, maybe we are bad at telling the difference between the two conditions.
• Diagnosis and classification of schizophrenia- evaluation 4

  There is considerable symptom overlap (Occurs when two or more conditions share symptoms) between SZ and e.g., bipolar disorder (delusions and avolition). Again calls into question the validity of classification and diagnosis. May be diagnosed w/ SZ under ICD but w/ bipolar disorder under DSM. Even suggests that they may not be two conditions but one.
• Diagnosis and classification of schizophrenia- evaluation 5

  Gender bias in diagnosis

  Longenecker et al. (2010) found that since the 1980s men have been diagnosed w/ SZ more often than women. May be genetic vulnerability or gender bias - women appear to typically function better than men (more likely to work and have good family relationships) which may mask symptoms.
• Diagnosis and classification of schizophrenia- evaluation 6

  Cultural bias in diagnosis

  African Americans are several times more likely than white people to be diagnosed w/ SZ, but may be due to culture bias. Positive symptoms such as hearing voices may be more acceptable in African cultures because of cultural beliefs in communication w/ ancestors, but when reported to a psychiatrist from a different cultural tradition these experiences could be seen as bizarre and irrational.