Reliability and validity in diagnosis and classification of schiz

Where is the DSM and ICD used?

• DSM - America

• ICD - Europe & other parts of the world

Why is the ICD & DSM used for?

• list all the possible mental disorders and their symptoms 

• Used by MH prof to decide whether someone is mentally ill & what kind of mental illness they might be suffering from

Why might a diagnosis of schiz using DSM/ICD not be reliable?

• Lack of time to spend on necessary interviews + rating scales

• Use of unstruct interviews meaning patients prov diff info to diff practitioners/ at diff times

• Subj interpret by MH professional based on what patient has said

What are the 2 ways to check reliability? Reliability = consistency

• inter-rater reliability 

• Test-retest reliability 

What is inter-rater reliability?

Different MH prof diagnose same patient, agreement on diagnosis shows high reliability

What is test-retest reliability?

• MH prof diagnoses patient twice, several weeks apart

• Assuming the patient’s symptoms have not changed, agreement on diagnosis shows high rel 

Why is there problems with reliability?

• Reliability = consistency

• whether diff MH prof can agree when a person is suffering from schiz

• or whether the same MH prof will produce the same schiz diagnosis overtime

Why is there problems with validity?

• validity = accuracy

• when MH prof diagnose a person with schizophrenia, do they really have schizophrenia, or could it be another illness?

Why might a diagnosis of schiz using DSM/ICD not be valid?

• Patients may not be honest ab their symp due to embarrassment/inaccurate or biased remembering

• MH prof may be biased in their thinking/perceptions

MH prof often found difficult to decide whether a symp should be considered ‘present’ / ‘absent’ as not clear how severe a symp should be or how often it should happen to be considered ’present’

Why is it important that a diagnosis is accurate?

• inaccurate diagn lead to incorrect treatm leading to side effects/patient getting worse

• can lead to stigmatisation + discrimination → can make the patient's life even harder