Issues in diagnosis; Validity

Question 1

Valid diagnosis

Answer 1

-A valid diagnosis is one that is accurate and true/ correct.

Question 2

In order for diagnoses to be correct 2 main conditions have to be satisfied;

Answer 2

• The illness has to be reliably defined / classified and diagnosed
• The illness has to be validly defined or classified

Question 3

How reliability relates to validity of diagnosis

Answer 3

• If the reliability of diagnosis is poor then so too is the validity.
• If there is inconsistency (lack of reliability) in diagnosis across clinicians at least one must be an invalid diagnosis.
• Reliability is not a guarantee of correctness.

Question 4

Rosenhan (1973)

Answer 4

Rosenhan’s (1973) study, in which pseudo- patients reported that they were hearing a voice saying ‘thud’ to doctors at psychiatric hospitals. All but one received a diagnosis of schizophrenia. In this case, the doctors were very reliable in their diagnoses, but they were invalid, i.e., wrong; none of the pseudo- patients had schizophrenia.

Question 5

Major problem

Answer 5

-In Sz there is no physiological indicator of illness; so all psychiatrists can do is observe behaviour

Question 6

Truth of diagnosis

Answer 6

• Reduced by low reliability
• Improved by increased reliability
• Relies on valid classification system
• Improvements in validity as a result of improvements in reliability?

Question 7

Invalid diagnosis =>

Answer 7

Wrong treatment

Question 8

Diagnosis =>

Answer 8

Labelling

Question 9

Truth of classification

Answer 9

• Is Sz a genuine, distinct disorder?
• Descriptive: do symptoms cluster?
• Aetiological: causes/ mechanisms
• Predictive: prognosis over time

Question 10

Invalid classification =>

Answer 10

Invalid diagnosis

Question 11

Swartz

Answer 11

This is shown in Swartz’s case study of an African –American woman who was wrongly prescribed antipsychotics for 10 years to treat hallucinations and agitation. An EEG later revealed evidence of epilepsy, and when the appropriate treatment (anticonvulsants) was given, her symptoms disappeared.

Question 12

Treatment

Answer 12

If psychiatrists are to treat schizophrenia properly they must be diagnosing it properly. If diagnoses are invalid two errors can occur;

• False positive
• False negative

Question 13

False positive

Answer 13

• If a patient is diagnosed with an illness that they do not have then they may receive treatment with powerful anti- psychotic drugs
• This may lead to the side effects of anti- psychotics, such as weight gain, sexual dysfunction and tardive dyskinesia
• Some argue that treating people with anti- psychotics when they don’t have Sz can sensitise dopamine receptors and induce the symptoms of Sz

Question 14

False negative

Answer 14

• If a patient is not diagnosed with an illness that they do have, then they will not receive treatment for an illness that they do have
• This leaves patients vulnerable and suffering unnecessarily

Question 15

Perlman (2000)

Answer 15

Perlman (2000) reported on patients (who it turned out had Asperger’s syndrome) diagnosed with undifferentiated schizophrenia, but did not fit the criteria properly: they had negative symptoms only. These patients were given unnecessary antipsychotics despite a lack of positive symptoms.

Question 16

Research

Answer 16

• If psychologists are to explain schizophrenia doctors to be diagnosing it properly, i.e., in a valid way
• If diagnoses are inconsistent or based on an invalid definition, explanations cannot be properly tested.

Question 17

Descriptive validity- are the symptoms right?

Answer 17

In the case of schizophrenia the diversity of symptoms makes it difficult to define precisely; this has been a major argument against the validity of classification of the illness. Individual patients can have little in common with each other yet have the same diagnosis. Kleitman points out that there is no pathognomonic (defining) symptom of schizophrenia.
The boundaries between schizophrenia and depression are often blurred, since they share many symptoms. Negative symptoms of schizophrenia, such as anhedonia, ‘the decreased ability to experience pleasure from positive stimuli’, sound very similar to a core symptom of depression, that the patient has ‘markedly diminished interest or pleasure in all, or almost all activities most of the day, nearly every day’. This suggests that the two disorders are not distinguished clearly enough, reducing the validity of classification.

Question 18

Aetiological validity- can we identify causes / mechanisms?

Answer 18

It is plausible to use evidence from causes or mechanisms to argue that an illness is well- defined. A problem with schizophrenia is that there is disagreement on its causes and the mechanisms involved.
However, Howes & Kapur (2008) argue that pre- synaptic dysregulation of dopamine is involved in all cases of schizophrenia that involve psychotic symptoms (i.e., hallucinations and delusions). They say that this is the common mechanism in all cases of schizophrenia, even if the initial cause of the dysregulation may be different in different cases. This suggests that if we restrict the term schizophrenia to those with psychotic symptoms, and that such symptoms are caused by dopamine dysregulation, that the disorder can be defined in a clearer way, i.e., such that there is a mechanism that is the same in all cases. If this claim were supported by research this would give the classification of schizophrenia much greater aetiological validity.

Question 19

Predictive validity- what is the prognosis / reaction to treatment?

Answer 19

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.

About 1/3 of patients remain chronically ill, about 1/3 recover from initial bouts of the illness and about 1/3 have periods of illness and periods of being relatively well. This shows that patients have very different histories and that it would be hard to predict who would have better outcomes.

Reaction to treatments for schizophrenia, especially drug treatments, is very mixed. All drugs that have any effectiveness are those that target dopamine receptors, but some are effective for some patients but not others, and prognosis is unpredictable.