diagnosis and classification of shizophrenia evaluation Flashcards
what is co-morbidity
the occurence of two disorders or conditions together, e.g. a person has schizophrenia and a personality disorder
Where two conditions are frequently diagnosed together it calls into question the validity of classifying the two disorders separetley
what is symptom overlap
occurs when two or more conditions share symptoms this calls into question the validity of classifying the two disorders separately
what is reliablity
reliability = consistency
an important measure of reliability is inter-rater reliability - the extent to which different assessors agree on their assessments
what does reliability mean for schizophrenia diagnosis
in the case of diagnosis, this means the extent to which two or more mental health professionals arrive at that same diagnosis for the same individual
what study shows that schizophrenia diagnosis and classification has poor reliability
Ellie Cheniaux et al had two psychiatrists independently diagnose 100 people uding both DSM and ICD criteria
Inter - rarter reliability was poor, with one psychiatrist diagnosing 26 with schizophrenia to DSM and 44 according to ICD, and the other diagnosing 13 according to DSM and 24 according to ICD.
This poor reliability is a weakness of the diagnosis of schizophrenia as it means that some people are misdiagnoses/overdiagnosed with one and undersiagnosis with the other.
what is validity
it is the extent to which we are measuring what we are intending to measure
what does validity mean for the diagnosis of schizophrenia
in the case of the mental disorder like schizophrenia there are number of validity issues to consider
how do we asses validity for schizophrenia diagnosis
one standard way to assess the validity of diagnosis is by seeing whether different assessment systems arrive at the same diagnosis for the same person
If we consider the figures in Cheniaux et al study, we can see that schizophrenia is being more likely diagnosed using ICD than DSM.
This suggests that schizophrenia is either over-diagnosed in ICD or underdiagnosed in DSM. Either way, this poor validity is a weakness for the diagnosis of schizophrenia
why is co-morbidity a limitation for schizophrenia diagnosis
if conditions occur together a lot of the time then this calls into question the validity of their diagnosis and classification because they might be a single condition
e.g. Peter Buckley et al (2009) concluded that around 1/2 of people with a diagnosis of schizophrenia have a diagnosis of depression (50%) or substance abuse (47%)
PTSD also occurs in 29% of cases and OCD in 23%
what do Buckley et al findings suggest
this poses as a challenge for both classification and schizophrenia are also diagnosed with depression as maybe we are just quite bad at telling the difference between the two conditions
In terms of classification, it may be that, if very severe depression looks like schizophrenia and vice versa, then they might be better seen as one single condition.
This confusing question is a weakness of the diagnosis and classification of diagnosis
why is symptom overlap a limitation for schizophrenia
there is considerable overlap between the symptoms of schizophrenia and other conditions
this calls into question the validity of the classification and diagnosis of schizophrenia
Under ICD a person might be diagnosed with schizophrenia; however, many of the same individuals would receive a diagnosis bipolar disorder according to DSM criteria
This is unsurprising given the overlap of symptoms. It even suggests that schizophrenia and bipolar disorder may not be two different conditions but one
why is cultural bias a limitation for schizophrenia
African American (AA) and English people of Afro - Carribean origin (A-C) are 7 times more likely to be diagnosed with schizophrenia
the rates in Africa and West Indies are not particularly high this is almost certainly not die to genetic vulnerability
Diagnosis seems to be beset with issues of culture bias
Javier Escobar has pointed out that (overwhelmingly white) psychiatrists may tend to over interpret symptoms and distrust the honesty of a Afro - Caribbeans during diagnosis
what are the genetic biological explanations for schizophrenia
- the genetic basis of schizophrenia
- the dopamine hypothesis
- neural correlates
what is the genetic basis of schizophrenia
- schizophrenia runs in the family
2. candidate genes
what does it mean when we say that schizophrenia runs in the family
schizophrenia runs in the family is relatively weak evidence in itself for a genetic link as family members tend to also share aspects of their environment as well as genes
However, there have been systematic investigations of the extent to which greater genetic similarity between family members is associated with the likelihood of both developing schizophrenia
what is some evidence to the genetic link of schizophrenia
we share 100% of our genes with identical twins and 50% with parent/sibling
There is a strong relationship between the degree of genetic similarity and shared risk of schizophrenia demonstrated in Grottesman study - as genetic similarity increases so does the probability if sharing schizophrenia
what are candidate genes
individual genes are believed to be associated with risk of inheritance because a number of genes each appear to confer a small increased risk of schizophrenia it appears that schizophrenia is polygenic - it requires a number of factors to work in combination
because different studies have identified different candidate genes it also appears schizophrenia to be aetiologically heterogeneous
what is aetiologically heterogeneous
different combinations of factors lead to the condition
what is a study to show that schizophrenia is polygenic
Ripke et al (2014) carried out a huge study combining all previous data from genome - widestudies of schizophrenia
The genetic make - up of 37,000 people diagnosed with schizophrenia was compared to 113,000 controls, 188 genetic variations were associated with increased risk of schizophrenia
Genes associated with increased risk included those coding for the functioning of a number of neurotransmitters
what is the dopamine hypothesis
it involves neurotransmitters which are brain’s chemical messenger’s appear to work differently in the brain of a person with schizophrenia
In particular dopamine (or DA) is widely believed to be involved
Dopamine is important in the functioning of several brain systems that may be implicated in the symptoms of schizophrenia
what are the two dopamine hypothesis
HYPERdopaminergia in the subcortex
HYPOdopaminergia in the subcortex
HYPERdopaminergia in the subcortex
this is the original version of the dopamine hypothesis focused on the possible role of high levels or activity of dopamine (hyperdoperminergia) in the subcortex, i.e, the centrak areas of the brain
e.g. an excess of dopamine receptors in Broca’s area (which is responsible for speech production) may be associated with poverty of speech and/ or experience of auditory hallucinations
HYPOdopaminergia in the subcortex
this is the more recent version of the dopamine hypothesis have focused instead on abnormal systems in the brains cortex
Goldman- Rakic et al (2004) have identified a role for low levels of dopamine (HYPOdopamiergia) in the prefrontal (responsible for thinking and decision making) in the negative symptoms of schizophrenia
it may be that both hyper and hypodopaminergia are correct explanations - both high and low levels of dopamine in different brain regions are involved in schizophrenia
what are neural correlates of schizophrenia
neural correlates are a measurements of the structure/ function of the brain that correlate with an experience, in this case schizophrenia schizophrenia
positive and negative symptoms have neural correlates
neural correlates of negative symptoms
an example of negative symptoms is avolition which is the loss of motivation
motivation involves the anticipation of a reward, and certain regions of the brain
motivation involves the anticipation of a reward, and certain regions of the brain
e.g. Ventural straitum are believed to be particularly involved in this
how is the ventral staitum linked to avolition
ventral striatum are believed to be particularly involved in this anticipation. It therefore follows that abnormality of areas like the ventral striatum may be involved in the development of avolition
who conducted a study looking at activity levels in the ventral striatum
Juckel et al (2006) have measured activity levels in the ventral striatum in schizophrenia and found lower levels of activity than those observed in controls in controls
Juckel et al observed a negative correlation between activity levels in the ventral striatum and the severity of overall negative symptoms
Thus activity in the ventral striatum is a neural correlate of negative symptoms
neural correlates of positive symptoms
positive symptoms also have neural correlates
Allen et al (2007) scanned the brains of people experiencing auditory hallucinations and compared them to a control group whilst they identified pre-recorded soeech as their or others
Lower activation levels in the separate temporalgyrus and anterior cingulate gyrus were found in the hallucination, which also make more errors than the control group.
We can thus say that reduced activity in these two areas of the brain is neural correlate of auditory hallucination
