Refers to consistency of measuring instrument, such as a questionnaire or
scale, to assess, for example, severity of their Sz symptoms
R can be measured in terms of whether 2 independent assessors give
similar diagnosis (inter-rater r) or whether tests used to deliver these
diagnosis are consistent over time (test-retest r)
A02
Unreliable sympotms
To be diagnosed w/ Sz, a person only has to have 1 of
characteristic sympotms if their 'delusions are bizarre'
Mojtabi + Nicholson
50 senior US psychiatrists were asked to differentiate between 'bizarre' + 'non-bizarre' delusions
They produce inter-reliability correlations of only around +40, forcing researchers to conclude even this central diagnostic requirement
lacks sufficient reliability for it to be reliable method of distinguishing between Sz + non-Sz patients
Cultural differences in diagnosis
Copeland
Gave 134 US + 194 British psychiatrists
a description of a patient
69% of US psychiatrists diagnosed Sz but only 2% of British psychiatrists gave same diagnosis
Reliability - Rosenhan
A01
Situational factors are supposedly more important than actual
characteristics of a person when it comes to diagnosis
A02
Demonstrated effect of 'situational' factors in study
'being sane in insane places'
Pseudo patients were sent into institutions + were classified as Sz
Claimed they heard an unfamiliar voice saying words 'empty', 'hollow' + 'thud'
Throughout stay, none of the staff
recognised they were actually normal
Some of them made notes of what was occurring while
omitted - staff took this as part of their Sz
Suggests situation is more important than actual person
Complication made more apparent...
Follow-up study
R warned hospitals of his intention to
send out more 'pseudo patients'
Resulted in 21% detection rate
Although none actually presented themselves
Validity
A01
Refers to extent a diagnosis represents something
that is real + distinct from other disrders
+ extent a classification system (ICD or
DSM) measures what it claims to
measure
R + V inextricably linked because diagnosis
cannot be valid if it isn't reliable
A02
Comorbidity
Refers to extent two (or more) conditions co-occur
Commonly found among patients diagnosed w/ Sz
Medical complications
Poor levels of functioning found in many Sz may be less result of
psychiatric disorder + more to do w/ untreated comorbid physical disorders
Weber et al
Examined nearly 6 million
hospital discharge records
Psychiatric + behaviour related diagnosis accounted for 45% of C
Many patients w/ primary diagnosis of Sz also diagnosed w/ med probs. -
asthma, hypertension + type 2 diabetes
Concluded consequence of being diagnosed w/ psychiatric
disorder such as Sz is patients tend to receive lower standard of
med care, which in adversely affects prognosis
Also found evidence of many comorbid
non-psychiatric diagnoses
Suicide risk
People w/ Sz pose relatively high risk for S, w/ comorbid
depression being major cause for suicidal behaviour
Among patients in National Comorbidity Survey, rate for attempted
suicide rose from 1% of those w/ Sz alone to 40% for those w/ at least 1
lifetime comorbid mood disorder
Predictive validity
A01
People diagnosed as Sz rarely share same symptoms, nor is there
evidence they share same outcomes
Prognosis for patients varies w/ about 20% recovering their previous level of
functioning, 10% achieving significant + lasting improvement + about 30%
showing some improvement w/ intermittent relapses
Diagnosis of Sz, therefore, has little PV - some people never
appear to recover from disorder, but many do
A02
Symptoms
Despite belief identification of symptoms of Sz would make
for more valid diagnoses of disorder, many symptoms also
found in other disorders
Ellason + Ross
People w/ dissociative identity disorder (DID) actually
have more Sz symptoms than people diagnosed as being
Sz!
Other factors linked to prognosis of disorder
Gender, ethnicity + psychosocial factors
M are supposedly more at risk than w
Harrison et al
Reported incidence rate for Sz was 8 times higher for
African-Caribbean groups than for white groups
Result of poor housing, higher rates of
unemployment + social isolation
Or result of cultural differences in language + mannerisms +
difficulties in relating between black patients + white
clinicians