classifications of schizophrenia

• schizophrenia 


  • 1% of the population have schizophrenia. Onset of first symptoms is typically around 15 to 45 years of age. Men are more likely to get schizophrenia, typically having an earlier onset.
• what is used to diagnose schizophrenia?


  • The Diagnostic and Statistical Manual (DSM) is most often used to diagnose schizophrenia. However the ICD (International Classification of Disease) can also be used. DSM-5 and ICD-10 are two separate systems/criteria for diagnosis.

  o DSM-5 requires one positive symptom.

  o ICD-10 requires two negative symptoms.
• positive symptoms of schizophrenia 


  additional experiences that are beyond those of normal experiences

  hallucinations: additional sensory experiences such as seeing distortions in objects that look like faces, or hearing voices

  delusions: irrational beliefs about themselves or the world, such as feelings of persecution or grandeur
• negative symptoms of schizophrenia 


  losses of normal experiences and abilities

  Avolition (a lack of purposeful behaviour. No energy to socialise or look after hygiene. Generally apathetic)

  Speech Poverty (Brief verbal communication style. Loss of quality and quantity of verbal responses. Can be classified as a positive symptom if speech is excessively disorganised with sufferers wandering off the point)

  catatonia (lack of movement)
• Reliability 


  the extent to which a finding is consistent. It is the extent to which psychiatrists can agree on the same diagnosis when independently assessing patients (inter-rater reliability)

  for a classification system to be reliable, the same diagnosis should be made each time - different psychiatrists should reach the same decision when assessing a patient
• test-retest reliability 


  if the same thing measured under the same conditions yields the same results every time, i.e: the same doctor giving the same diagnosis over time for the same symptoms.
• Inter-rater reliability of schizophrenia diagnosis is often low


  Beck (1962): found only a 54% concordance rate between doctors’ assessments of 153 patients. Inter-rater reliability of schizophrenia diagnosis is often low

  • However Jakobsen et al. (2005) tested the reliability of the ICD-10 classification system in diagnosing schizophrenia. A hundred patients were assessed , and a concordance rate of 98% was obtained. This demonstrates the high reliability of the clinical diagnosis of schizophrenia using up-to-date classification.
• Validity


  the extent to which we are measuring what we are intending to measure. In the case of an illness like schizophrenia we have to consider the validity of the diagnostic tools
• comorbidity


  Comorbidity is when a person has more than one mental condition

  Buckley (2009) found that 50% of schizophrenics are also diagnosed with depression, 47% with drug abuse, and 29% with PTSD, and 23% with OCD. So conditions like severe depression could be being misdiagnosed as schizophrenia. Or, as these diagnoses often happen together, perhaps they are not even separate disorders
• symptom overlap

  • Other disorders like bipolar disorder have hallucinations and delusions as positive symptoms as well. If two disorders are very similar then it may be questions if they actually are distinct disorders
  • Ellason and Ross (1995): a total 108 patients with a clinical diagnosis of DID were assessed from sz symptoms. Findings: patients with this disorder reported more positive symptoms of sz than diagnosed schizophrenics - reduces validity
• gender bias 


  Another issue with schizophrenia is gender bias. It may be that men are more likely to be diagnosed due to gender bias as women’s issues aren’t taken as seriously

  Fischer and Buchanan (2017): ratio of 1.4:1 for men to women. suggesting gender bias

  Cotton et al (2009) suggests that women could just have better coping strategies and so don’t access treatment as often as men.

  • Lewin (1984) found that the number of female sufferers reduced when clearer diagnostic criteria were used, meaning that clinicians were overdiagnosing women.
• cultural bias 


  Cochrane (1977) found that the rate of diagnosis of schizophrenia in the UK for afro-caribbean people was 7%, compared to 1% for the general Uk population and 1% for afro-caribbeans in the caribbean.

  Harrison et al (1997) found that diagnosis of sz amongst African American populations were 8x more common
• Rosenhan's experiment on Schizophrenia diagnosis

  • 8 pseudopatients (confederates) visited hospitals posing symptoms of hallucinations - gave real life histories. they acted normally - staff observed
  • 11 diagnosed with SZ, 1 with manic-depression
  • staff failed to distinguish sane from insane, questioning reliability and validity of diagnoses of schizophrenia