Classification & diagnosis of Sz

Reliability
1. For diagnosis to be of any use
  1. Must be reliable
  2. Must be consensus in way people diagnosed
2. Qs & scales can be measured
  1. Whether 2 independent assessors give similar diagnosis (inter - rater) / whether tests to deliver diagnosis consistent over time (test - retest)
Validity
1. Extent which diagnosis reps something real & distinct from other disorders
  1. Extent that classification system - ICD / DSM - measure what claims to measure
2. Reliability & validity = linked
  1. If scientists can't agree what Sz is (validity) how can they accurately / consistently diagnose it (reliability)
Low predictive validity
1. Little predictive validity
  1. Diagnosis not helpful in dealing w/ outcomes / treatment
  2. Prognosis varies massively
2. 20% recover to prev lvls of functioning, 10% achieving lasting improvements, 30% some improvements w/ relapses
3. Malmberg et al (1998)
  1. Prognosis more to do w/ gender
4. Harrison et al (2001)
  1. Prognosis more to do w/ psychosocial factors
Comorbidity (validity)
1. Fairly common to show symptoms of 2 mental disorders simultaneously
  1. Sz can be accompanied by depression
2. Clinicians make dual diagnosis - appropriate treatment for both disorders
Symptom overlap (validity)
1. Some of Sz symptoms found in many other disorders
  1. Depression & bipolar disorder
  2. Affects validity of diagnosis
2. Differential diagnosis
  1. Diff to define boundaries between Sz & other disorders
    1. Mood disorders, personality & developmental disorders - autism
    2. People w/ temporal lobe epilepsy often show similar symptoms to Sz
3. Becomes dimensional disorder
  1. Degree of prob hearing voices (coping strategies
Inter rate reliability
1. Low in earlier versions of DSM, attempts made make US & EU versions made consistent
2. Remains relatively low
3. Vague criteria for diagnosis (bizarre delusions)
  1. Leads to incorrect diagnosis
    1. Result of probs w/ defining Sz
      1. If you cannot classify Sz how do you diagnose it?
Cultural variations (reliability)
1. Although Sz occurs across cultures
  1. Finding in USA / Uk = more freq among African American & African Caribbean pops
2. Not clear what this reflects
3. In some Asian cultures, a person experiencing some emotional turmoil is praised & rewarded if they show no expression of their emotions
4. In certain Arabic cultures, outpouring of public emotion is understood & often encouraged
  1. W/out this knowledge an individual displaying overt emotional behaviour may be seen = abnormal
Rosenhan 1973 'On being sane in insane places'
1. Aimed
  1. Test hypothesis that psychiatrists cannot reliably tell diff between people who are sane & those who aren't
2. Highlighted unreliability of diagnosis
3. But was over 40 yrs ago, lots have changed
Why does this matter? What are the implications?
1. Japan - Sz literally translates to 'disease of the disorganised mind'
  1. Stigma of this is so great that psychiatrists are reluctant to tell patients of their cond
  2. Result - 20% of those w/ Sz are actually aware of it, while other 80% are left undiagnosed
    1. Kim & Berrios (2001)
How useful is a diagnosis of Sz?
1. Not helpful label (psychosis)
2. No universally agreed definition
3. Life long cond / label
4. Classification systems can be dangerous (marginalise those who don't fit w// society)
5. If we don't know what it is, how can we decide who has it?

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Classification & diagnosis of Sz

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