Discuss issues associated with the classification and / or diagnosis of schizophrenia. (8+16)

Question 1

Reliability of Diagnosis (AO1)

Answer 1

Differences in procedures, differences in clinicians, differences between patients

Question 2

Differences in procedures

Answer 2

e.g. use of classification systems - if clinicians use different classification systems or other criteria they are more likely to make different diagnoses. DSM is the dominant manual in the US, while a mixture of diagnostic systems are used in the rest of the world

Question 3

Cooper

Answer 3

American and British psychologists were shown the same videotaped clinical interviews and asked to make a diagnosis. The New York psychiatrists diagnosed schizophrenia twice as often and the London psychiatrists diagnosed mania and depression twice as often

Question 4

Cheniaux

Answer 4

Rates of diagnosis using ICD 68/200 were significantly higher than when using DSM-IV 39/200

Question 5

Differences between clinicians

Answer 5

e.g. subjective interpretation - even if the same classification systems are being used, clinicians may interpret them differently. Many phrases in manuals are open to interpretation

Question 6

Mojtabi and Nicholson

Answer 6

Weak inter-rater reliability (0.4) between clinicians in judgements of whether hallucinations were ‘bizarre’ or not

Question 7

Difference between patients

Answer 7

Patients may present differently on different days, depending on their mood and the variability of symptoms. A diagnosis on one day could be different from that on another day, depending on the symptoms and their severity. Patients may also react differently depending on the doctor (characteristics: age, gender, attractiveness)

Question 8

Reliability of diagnosis (AO2)

Answer 8

Improvements in reliability over time

Question 9

Beck

Answer 9

early research showed worryingly low reliability - two psychiatrists to diagnose 154 patients. It was found that the inter-rater reliability was as low as 54% (testing reliability of DSM 2)

Question 10

Reliability improved with DSM 3

Answer 10

removed vague descriptions and blurred boundaries between disorders, and clarifying how many symptoms, and of which type was needed - field studies found high levels of reliability, diagnoses were consistent 81% of cases

Question 11

Cheniaux (k)

Answer 11

found kappa statistics of 0.59 for DSM-4 and 0.56 for ICD-10 - the kappa statistic between DSM 4 and ICD 10 was 0.61 (good = 0.4-0.7)

Question 12

Field studies for DSM 5

Answer 12

found lower reliability, but this is explained by the tougher trials that were carried out: patients were assessed under real life conditions rather than in idealised laboratory conditions - kappa statistic 0.46

Question 13

Validity of diagnosis (AO1)

Answer 13

Descriptive validity, Aetiological validity, Predictive validity

Question 14

Descriptive validity

Answer 14

Are the symptoms right? It is usually possible to define medical illnesses by their symptoms

Question 15

Aetiological validity

Answer 15

Can we identify causes/mechanisms? It is plausible to use evidence from causes or mechanisms to argue that an illness is well-defined

Question 16

Predictive validity

Answer 16

What is the prognosis/reaction to treatment? In a well-defined illness we should be able to describe how the illness progresses over time and predict how they will react to treatments

Question 17

Validity of Diagnosis (AO2)

Answer 17

Rosenhann, Liddle

Question 18

Rosenhann

Answer 18

Reliability is not a guarantee of validity; Rosenhann - pseudo-patients reported that they were hearing voices to doctors at psychiatric hospitals. All but one received a diagnosis of schizophrenia . In this case, all of the doctors were very reliable in their diagnoses, but they were invalid, as none of the pseudo-patients had schizophrenia

Question 19

Liddle

Answer 19

Supports doubts raised over descriptive validity - he found 3 clusters of symptoms, positive, negative and symptoms of cognitive disorganisation - this suggests that classification of schizophrenia as a single illness is problematic, and that distinctions within it are needed

Question 20

Swartz

Answer 20

invalid diagnoses have serious implications for treatment - false positive - African-American woman who was prescribed with antipsychotics for 10 years to treat hallucinations and agitation. An EEG later revealed evidence of epilepsy, and when the appropriate treatment was given, her symptoms disappeared

Question 21

A false-negative

Answer 21

if a patient is left undiagnosed with an illness they have, then they will fail to receive the necessary treatment

Question 22

A false-positive

Answer 22

may also have negative effects on the person - the label ‘schizophrenic’ might become part of the person’s identity - they might accept this label and in a self-fulfilling prophecy, develop symptoms of illness or deteriorate in functioning