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the feeling that thoughts or feelings have been inserted or withdrawn from the mind.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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Reliability
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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Validity
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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