Discuss validity and reliability of diagnosis.

Validity: pertains to if the diagnosis reflects a genuine disorder
Reliability: means that different diagnosticians agree on the same diagnosis

Validity: 2 studies showing how diagnoses don't always show a genuine disorder
1. Chapman & Chapman (1967):
Beginning clinicians observed draw-a-person test drawing randomly paired (unknowingly to participants) with symptom statements of patients.

Although the relationship between symptoms and drawings were absent, participants rated a high associative strength between symptom and drawing characteristics (e.g. paranoia and drawing big eyes)
This study therefore shows how diagnoses don't always reflect genuine disorders. They also depend heavily on dispositional instead of situational factors.
2. Rosenhan (1973)

Eight ‘sane’ people (3 women & 5 men from a variety of occupational
backgrounds) arranged appointments at various hospitals and complained that they had been hearing voices. The voices were unclear, unfamiliar, of the same sex and said single words like empty, hollow and thud.

The pseudo-patients did not change any aspect of their behaviour, personal history or circumstances (apart from their names). On admission to the hospital ward every pseudo-patient immediately stopped simulating any symptoms and responded normally to all instructions (except that they did not swallow any medication) and said they were fine, experiencing no more symptoms and would like to be released.

All but one pseudo-patients were admitted to a hospital with a diagnosis of schizophrenia and their ‘sanity’ was never detected by staff although many other patients did become suspicious! Length of stay ranged from 7 days to 52 days with an average of 19 days. All except one were released with a diagnosis of ‘Schizophrenia in remission’ supporting the view that they had never been detected as ‘sane’ at all.

A follow up study was conducted to check the poor reliability of diagnosis, whereby a teaching hospital was told to expect pseudo-patients over a three month period. Not a single pseudo-patient ventured near the hospital, but 41 genuine patients were suspected of being fakes, 19 of these were suspected by a psychiatrist and another member of staff.

Reliability: 2 studies showing how diagnostic classification systems can easily be unreliable

1. Cooper et al (1972)
Found New York psychiatrists were twice as likely to diagnose schizophrenia than
London psychiatrists, who in turn were twice as likely to diagnose mania or depression
when shown the same videotaped clinical interviews.

2. Beck et al (1962)
Found that agreement on diagnosis for 153 patients between two psychiatrists was
only 54%. This was often due to vague criteria for diagnosis.