Classification & diagnosis of Sz

Classification & diagnosis of Sz

1. Reliability

   • For diagnosis to be of any use
     • Must be reliable
     • Must be consensus in way people diagnosed
   • Qs & scales can be measured
     • Whether 2 independent assessors give similar diagnosis (inter - rater) / whether tests to deliver diagnosis consistent over time (test - retest)

2. Validity

   • Extent which diagnosis reps something real & distinct from other disorders
     • Extent that classification system - ICD / DSM - measure what claims to measure
   • Reliability & validity = linked
     • If scientists can't agree what Sz is (validity) how can they accurately / consistently diagnose it (reliability)

3. Low predictive validity

   • Little predictive validity
     • Diagnosis not helpful in dealing w/ outcomes / treatment
     • Prognosis varies massively
   • 20% recover to prev lvls of functioning, 10% achieving lasting improvements, 30% some improvements w/ relapses
   • Malmberg et al (1998)
     • Prognosis more to do w/ gender
   • Harrison et al (2001)
     • Prognosis more to do w/ psychosocial factors

4. Comorbidity (validity)

   • Fairly common to show symptoms of 2 mental disorders simultaneously
     • Sz can be accompanied by depression
   • Clinicians make dual diagnosis - appropriate treatment for both disorders

5. Symptom overlap (validity)

   • Some of Sz symptoms found in many other disorders
     • Depression & bipolar disorder
     • Affects validity of diagnosis
   • Differential diagnosis
     • Diff to define boundaries between Sz & other disorders
       • Mood disorders, personality & developmental disorders - autism
       • People w/ temporal lobe epilepsy often show similar symptoms to Sz
   • Becomes dimensional disorder
     • Degree of prob hearing voices (coping strategies

6. Inter rate reliability

   • Low in earlier versions of DSM, attempts made make US & EU versions made consistent
   • Remains relatively low
   • Vague criteria for diagnosis (bizarre delusions)
     • Leads to incorrect diagnosis
       • Result of probs w/ defining Sz
         • If you cannot classify Sz how do you diagnose it?

7. Cultural variations (reliability)

   • Although Sz occurs across cultures
     • Finding in USA / Uk = more freq among African American & African Caribbean pops
   • Not clear what this reflects
   • In some Asian cultures, a person experiencing some emotional turmoil is praised & rewarded if they show no expression of their emotions
   • In certain Arabic cultures, outpouring of public emotion is understood & often encouraged
     • W/out this knowledge an individual displaying overt emotional behaviour may be seen = abnormal

8. Rosenhan 1973 'On being sane in insane places'

   • Aimed
     • Test hypothesis that psychiatrists cannot reliably tell diff between people who are sane & those who aren't
   • Highlighted unreliability of diagnosis
   • But was over 40 yrs ago, lots have changed

9. Why does this matter? What are the implications?

   • Japan - Sz literally translates to 'disease of the disorganised mind'
     • Stigma of this is so great that psychiatrists are reluctant to tell patients of their cond
     • Result - 20% of those w/ Sz are actually aware of it, while other 80% are left undiagnosed
       • Kim & Berrios (2001)

10. How useful is a diagnosis of Sz?

    • Not helpful label (psychosis)
    • No universally agreed definition
    • Life long cond / label
    • Classification systems can be dangerous (marginalise those who don't fit w// society)
    • If we don't know what it is, how can we decide who has it?