- Refers to the accuracy and objectivity of the info gathered
- Different disorders have different symptoms, these symptoms should not overlap.
- Esyenck found 2/3rds of patients with anxiety disorder had one or more additional anxiety disorders
If some people have a few different disorders because they have similar symptoms then it may question VALIDITY of diagnosis.....are they really different or should they only be one disorder?
- Specific treatments are made for different diagnosis'
- If diagnosis = valid, treatment should work
- Heather (1976) pointed out:
only 50% chance of predicting which treatments will be given from diagnosis
Howerver, some cases there is predictive validity:
- Schizphrenic patients = improve when given neuroleptic drugs, other patients don't (specific)
- Syndromes have specific causes
- Expect all those with the same disorder to have developed condition for the same reason
- NOT TRUE- many different reasons for disorders
E.g; Schizophrenia can have genetic basis in some cases but not in others
- Suggests the dianostic system is inadequate- can't all have the same causes
- Extent to which diagnoses agree from 2 different systems (DSM and ICD)
- Patient would be diagnosed the same in all the books
Andrews et al. (1999)
- assessed 1500 people using DSM-IV and ICD-10
- Found 68% agreement when diagnosing depression