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Classification and Diagnosis of
Schizophrenia…read more

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Characteristics of schizophrenia
Positive and Negative symptoms ­ Positive symptoms are those that appear to reflect an
excess or distortion of normal functions. Negative symptoms are those that appear to reflect
a diminution or loss of normal functions, which persist during periods of low (or absent)
positive symptoms
Positive symptoms
· Delusions ­ bizarre beliefs that seem to be real Negative symptoms
to the person with sz, but they aren't. These · Affective flattening ­ reduction in
delusions can be paranoid in nature, they may the range and intensity of
also include inflated beliefs about the persons emotional expression
power and importance · Alogia ­ Poverty of speech,
· Experiences of control ­ They may believe they characterised by the lessening of
are under control of an alien force that has speech fluency and productivity.
invaded their mind and/or body This is thought to reflect slowing or
· Hallucinations ­ bizarre, unreal perceptions of blocked thoughts
the environment that are usually auditory but · Avolition - The reduction of, or
may also be visual, olfactory or tactile inability to initiate and persist in,
· Disordered thinking ­ feeling that thoughts goal-directed behaviour (sitting in
have been inserted or withdrawn from the the house for hours everyday); is
mind. People may things that their thoughts often mistaken for apparent
are being broadcast so that others can hear disinterest
them…read more

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Evaluation ­ reliability
Reliability Inter-rater reliability ­ little evidence that DSM is
Refers to the consistency of a routinely with high reliability with mental health
measuring instrument, such as a clinicians. Whaley ­ inter-rater reliability
questionnaire or scale to assess, for correlations in the diagnosis of sz as low as +11
example, the severity of their sz Unreliable symptoms ­ for diagnosis of sz, only one
symptoms of the characteristic symptoms is required (bizarre
Inter-rater reliability ­ DSM III was delusions) ­ 50 psychiatrists in the US were asked to
specifically designed to provide a state the difference between `bizarre' and `non-
much more reliable system for bizarre' delusions, the produced inter-rater
classification of psychiatric disorders reliability correlations of only around +40
­ led to greater agreement over who Test-retest ­ Prescott ­ analysed the test-retest
did, and who didn't have sz (Carson) reliability of several measures of attention and
Test-retest reliability ­ Cognitive information processing in 14 chronic sz.
tests such as RBANS are important in Performance on these measures were stable over a
the diagnosis of sz as they measure 6-month period
the degree of neuropsychological Comparing DSM and ICD ­ Even though inter-rater
impairment. Test-retest reliability reliability was above +50 for both classification
was high at .84 (Wilks) systems, schizophrenia was more frequently
diagnosed in the ICD…read more

Slide 4

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Validity Evaluation ­ Validity
Refers to the extent that a diagnosis Comorbidity and medical complications ­
represents something that is real and poor levels of functioning in sz patients may
distinct from other disorders and the extent be less the result of their disorder and more to
to which that a classification system such as do with their untreated comorbid physical
the ICD or DSM measures what it claims to disorder. Weber ­ many patients with sz were
measure also diagnosed with medical problems, they
Comorbidity ­ refers to the extent that or concluded that a consequence of being
more conditions co-occur. Common among diagnosed with sz is that patients tend to
sz patients. Include substance abuse, receive a lower standard of medical care,
anxiety and symptoms of depression ­ which in turn affects their prognosis
Buckley estimated that comorbid Comorbidity and suicide risk ­ high suicide
depression occurs in 50% of patients, and risk in sz patients, with comorbid depression
47% of patients also have a lifetime being a major cause. 1% schizophrenia alone,
diagnosis of comorbid substance abuse 40% for those with at least one lifetime
Positive or negative symptoms -Positive comorbid mood disorder
symptoms more useful for diagnosis of sz Ethnicity may lead to misdiagnosis ­ rates of
than negative ­ Germany sz much higher among African-Caribbean's ­ 8
Prognosis ­ Little predictive validity, some times higher ­ poor housing, higher rates of
patients never appear to recover from the unemployment and social isolation, cultural
disorder but many do but with relapses differences in language and mannerisms…read more


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