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Type 1 Symptoms

  • characterised by positive symptoms, where something is added to the sufferer's personality.
    • delusions
      • bizarre beliefs that seem real but aren't.
    • experiences of control
      • the belief that you are under the control of an alien force.
    • hallucinations
      • unreal perceptions of the environment; usually auditory.
    • disordered thinking
      • the feeling that thoughts or feelings have been inserted or withdrawn from the mind.
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Type 2 Symptoms

  • characterised by negative symptoms, where something is removed from the sufferer's personality.
    • avolition
      • reduction or inability to engage in goal orientated behaviour.
    • affective flattening
      • reduction in the range and intentisty of emotional expression.
    • alogia
      • poverty of speech.
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  • consistency of measuring instruments. Can be measured in terms of whether two independent assesssors give similar diagnoses (inter-rater reliability) or whether tests used to deliver the diagnoses are consistent over time (test-retest reliability).
  • inter-rater reliability
    • DSM-III designed to provide much more reliability for diagnosing psychiatric disorders.
  • test-retest reliability
    • Wilks et al: administered two forms of the RBANS test to Sz patients over intervals of between 1 and 134 days. Test-retest reliability was +0.84.
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Reliability - Evaluations

  • inter-rater relability
    • Whaley et al: found inter-rater relability correlations for the DSM-III as low as +0.11 for the diagnosis of Sz.
  • test-retest reliability
    • Prescott et al: measured the test-retest reliability of several measures of attention and information processing in 14 chronic schizophrenics. Performance was stable over a 6-month period.
  • unreliable criteria
    • for a Sz diagnosis, only one of the symptoms is required if 'delusions are bizarre'.
      • Mojtabi & Nicholson: 50 senior American psychiatrists differentiated between 'bizarre' and 'non-bizarre' delusions. Produced inter-rater reliability of +0.40. Even this central diagnostic requirement lacks sufficient reliability to be useful.
  • cultural differences
    • Copeland et al: gave 135 US and 195 British psychiatrists a description of a patient. 69% of US psychiatrists but only 25 of UK psychiatrists diagnosed Sz.
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  • the extent to which a classification system actually measures what it claims to.
  • comorbidity
    • the extent that two or more conditions co-occur.
    • common among schizophrenics and include anxiety, depression and substance abuse.
    • Buckley et al: comorbid depression occurs in 50% of Szs. 47% also have a lifetime diagnosis of comorbid substance abuse.
  • prognosis
    • Szs rarely share the same symptoms or outcomes.
    • Bentall et al: 30% showed some improvement with intermittent relapses, 20% recovered their previous level of functioning and 10% achieved significant and lasting improvements.
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Validity - Evaluations

  • comorbidity and medical complications
    • Weber et al: examined 6 million hospital discharges. Psychiatric diagnoses accounted ror 45% of comorbidity. Many with a primary Sz diagnosis were also diagnosed with the likes of asthma and Type 2 diabetes. Patients with a psychiatric disorder tended to receive a lower standard of medical care.
  • comorbidity and suicide
    • Szs pose a relatively high risk for suicide.
    • Kessler et al: suicide rates rose from 1% for those with Sz alone to 40% for those with at least one lifetime comorbid mood disorder.
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Biological Explanations - Genetics

  • prevalence of Sz is the same all over the world (1%), which supports a biological view, as prevalence does not vary with the environment.
  • twin studies
    • Gottesman & Shields: 210 MZ (identical) and 319 DZ (fraternal) twins. MZ twins: 58% concordance, or 91% if one twin was severely affected. DZ twins: 26% concordance.
    • Joseph et al: meta-analysis. 40.4% concordance for MZ twins, and 7% for DZ twins.
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