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Reliability and Validity in Diagnosis and Classification - Coggle Diagram
Reliability and Validity in Diagnosis and Classification
Co-morbidity:
When one or more additional disorders or diseases occur with schizophrenia - can cause further confusion when diagnosing the illness
Peter Buckely (2009) - Schizophrenia is co-morbid with depression, substance abuse, PTSD and OCD. Results question whether schizophrenia should be seen as separate conditions to depression (50% co-morbid)
Culture and gender bias:
Gender bias
- the tendency for diagnostic criteria to be applied differently to males and females
It has been thought that schizophrenia rates are fairly equal amongst males and females, but psychologists disagree
Women are more likely to have co-morbidity
Negative symptoms are more likely to occur in males
Onset is later in women due to the oestrogen hypothesis (female hormones delay the onset, allowing them to finish schooling and build a life)
Women respond to lower dosages and, because they are usually on many more different medications than men and have a more active immune system, they experience more adverse effects
Cultural bias
- occurs when we over diagnose a condition in a specific culture
In Britain schizophrenia is commonly over diagnosed in Afro-Caribbean communities (they are also more likely to spend time in secure hospitals or wards)
Escobar suggests psychiatrists (who are overwhelmingly white male) over interpret symptoms and distrust the honesty of black people during diagnosis
Fernando (1992) identifies 5 key issues from studies of ethnicity and mental health
Over diagnosis among West Indian and Asian-British
Excessive use of compulsory admission for West Indian patients
More West Indian, African and Asian-British patients are transferred to locked wards when hospitalised
Excessive admissions of 'offender' patients among West Indian-British population
Over use of ECT among Afro-Caribbean and Asian-British patients
Symptom overlap:
Schizophrenia is a condition which has many similarities to other mental illnesses - this makes it difficult to diagnose a condition
eg. Schizophrenia has overlap symptoms with Bipolar, Autism and cocaine use
Affects descriptive validity
Diagnostic criteria:
DSM - USA
Requires 6 months of symptoms
Considers social issues
Asks for two or more major symptoms
Classifies + and - together
ICD - UK/EU
Requires 1 month of symptoms
Asks for one major symptom
ICD separates + and -
Problems these differences cause when diagnosing the disorder:
Moving countries
Long time to wait for treatment
Unreliable, invalid, inappropriate treatment given
Subjective interpretation
Over diagnosis
Unreliable, invalid, inappropriate treatment given
Reliability and Validity in Diagnosis:
Inter-rater Reliability
: Different clinicians make identical independent diagnosis at the same time
Test-retest Reliability
: The same or different clinicians make the same diagnosis on separate occasions
Predictive Validity
: If the treatment given is successful their diagnosis is valid
Descriptive Validity
: If patients who have schizophrenia have similar symptoms and these are different from other disorders the diagnosis is valid
Criterion Validity
: If different systems arrive at the same diagnosis then it is valid
Research shows inter-rater and test-retest reliability in diagnosis of schizophrenia is high
Recent change due to development in the DSM system
Osorio et al (2019) report that there is an excellent reliability for schizophrenia when using the same diagnostic system
In a sample of 180 individuals, pairs of interviewers achieved inter-rater reliability of +0.97 and test-retest reliability of +0.92
Rosenhan (1973) On being sane in insane places
Pseudo patients were admitted into psychiatric institutions after reporting that they had heard a voice on one occasion. During their stay in the institutions they were all diagnosed with schizophrenia
Once admitted into hospital they all behaved in a 'normal' way
They had to remain in hospital until staff felt that they had recovered enough to leave. Average stay was 19 days (7-52 day range)
This study demonstrated that diagnosis of schizophrenia in the 1970s WAS RELIABLE 9all were diagnosed with schizophrenia) but WAS NOT VALID (none actually suffered from schizophrenia)
Research shows that criterion validity in diagnosis is low:
Cheniaux et al (2009) used two psychiatrists to independently diagnose 100 patients using both DSM and ICD
Schizophrenia is more likely to be diagnosed using ICD than DSM in both cases so it shows that there is a low criterion validity in diagnosis
It is either over or under diagnosed in one of the systems