schizophrenia - reliability and validity in sz diagnosis

reliability and validity in sz diagnosis

positive symptoms

not usually present n a neurotypical individual

they reflect an excess or distortion of normal functioning

negative symptoms

characteristics that reflect a decrease in normal functions, such as reduced emotional expression, lack of motivation, and social withdrawal.

test-retest reliabiilty

doctors must be able to reach the same conclusion about a patient at 2 different points in time. the DSM and other tests must enable this to occur so a patient isnt labelled with a diagnosis

inter-rater reliability

the extent to which some different assessors agree on their assessments

doctors must reach the same conclusions about a patients diagnosis

Cheniaux (2009)

This research suggests that:

had 2 psychiatrists independently diagnose 100 patients using the DSM criteria and the ICD criteria. One doctor diagnosed 26 patients with sz according to the DSM and 44 according to the ICD. The other doctor diagnosed 13 according to DSM and 24 according to ICD.

the inter-rater reliability of classification system is poor because we would expect the same number of diagnosis made irrespective of criteria used.

AO3: cultural differences in diagnosis

• variation between countries when it comes to diagnosing sz

• Copelan (1971) 134 US and 194 UK psychiatrists a description of a patient. 69% of US psychs diagnosed sz, but only 2% of UK did

Research support: Rosenhan

aim: investigate how situational factors effect diagnosis

method: 8 patients went to 2 diff hospitals in the US and reported hearing voices. Once admitted they stopped stimulating symptoms

results: all patients admitted with a diagnosis of sz, one admitted with manic depression. Patients were kept in for periods of 7-52 days, average stay was19.

VALIDITY: the correctness of a diagnosis

AO3: gender bias

• occurs when accuracy of a diagnosis is dependent on the gender of an individual

symptom overlap

• many of the symptoms of sz are also found in other disorders such as depression and bipolar

• Read (2004) states that most with sz have sufficient sympoms of other disorders that they could also receive at least one other diagnosis

Co-morbitity

• Refers to the extent that 2 or more conditions co-occur

• sz often occurs alongside substance abuse, depression and anxiety.