Issues in Diagnosis and Classification Flashcards
Strength - Good reliability.
Reliability means consistency.
A psychiatric diagnosis is said to be reliable when different diagnosing clinicians reach the same diagnosis for the same individual (inter-rater reliability) and when the same clinician reaches the same diagnosis for the same individual on two occasions (test-retest reliability).
Prior to DSM-5, reliability for schiz was low but now has improved.
Osorio et al (2019) report excellent reliability for the diagnosis of schiz in 180 individuals using the DSM-5; pairs of interviewers achieved inter-rater reliability of +.97 and test-retest reliability of +.92.
This means that we can be reasonably sure that the diagnosis of schiz is consistently applied.
Limitation - Its co-morbidity with other conditions.
If conditions occur together a lot of the time then this calls into question the validity of their diagnosis and classification because they might actually be a single condition.
Schiz is commonly diagnosed with other conditions.
E.g. one review found that about half of those diagnosed with schiz also has a diagnosis of depression or substance abuse.
This is a problem for classification because it means schiz may not exist as a distinct condition, and is a problem for diagnosis as at least some ppl diagnosed with schiz may have unusual cases of conditions like depression.
Limitation (includes counterpoint): Low validity.
Validity concerns whether we assess what we are trying to assess.
One way to assess validity of a psychiatric diagnosis is criterion validity; Cheniaux et al (2009) had two psychiatrists independently assess the same 100 clients using ICD-10 and DSM-4 criteria and found that 68 were diagnosed with schiz under the ICD system and 39 under DSM.
This suggests that schiz is either over- or underdiagnosed according to the diagnostic system; either way this suggests that criterion validity is low.
In the Osorio et al study reported above there was excellent agreement between clinicians when they used two measures to diagnose schiz both derived from the DSM system. This means that the criterion validity for diagnosing schiz is actually good provided it takes place within a single diagnostic system.
Limitation: Existence of gender bias in diagnosis.
Since the 1980s men have been diagnosed with schiz more commonly than women (Fischer and Buchanan 2017). One possible explanation for this is that women are less vulnerable than men, perhaps because of genetic factors.
However it seems more likely that women are underdiagnosed because they have closer relationships and hence get support (Cotton et al 2009). This leads to women with schiz often functioning better than men,
This underdiagnosis is a gender bias and means women may not therefore be receiving treatment and services that might benefit them.
Limitation: Existence of culture bias in diagnosis.
Some symptoms of schiz, particularly hearing voices, have different meanings in different cultures. E.g. in Haiti some ppl believe that voices actually are communications from ancestors. British people of African-Carribean origin are up to nine times as likely to receive a diagnosis as white British people (Pinto and Jones 2008), although ppl living in African-Carribean countries are not, ruling out a genetic vulnerability.
The most likely explanation for this is culture bias in diagnosis of clients by psychiatrists from a different cultural background. This appears to lead to an overinterpretation of symptoms in black British people (Escobar 2012).
This means that British African-Carribean ppl may be discriminated against by a culturally-biased diagnostic system.
Limitation: Symptom overlap with other conditions.
There is considerable overlap between the symptoms of schiz and the symptoms of other conditions.
For example, both schiz and bipolar disorder involve positive symptoms (such as delusions) and negative symptoms (avolition).
In terms of classification this suggests that schiz and bipolar disorder may not be two different conditions but variations of a single condition. In terms of diagnosis it means that schiz is hard to distinguish from bipolar disorder.
As with co-morbidity, symptom overlap means that schiz may not exist as a distinct condition and that even if it does it is hard to diagnose, so both its classification and diagnosis are flawed.
