Biological Explanations Of Schizophrenia Flashcards
What have family studies confirmed about SZ?
That the risk of SZ increases in line with genetic similarity to a relative with the disorder.
What does it mean that SZ is polygenic?
That a number of different genes are involved.
What genes are most likely coding for SZ?
Neurotransmitters including dopamine.
What did Ripke et al do?
Combined all previous data from genome-wide studies of SZ.
How did Ripke et al compare data?
Compared the genetic makeup of 37,000 people with SZ to that of 113,000 controls.
108 separate genetic variations were associated with slightly increased risk of SZ.
Why does SZ appear to be aetiologically heterogeneous?
Because different studies have identified different candidate genes.
In the absence of family history with SZ what can SZ also have?
A genetic origin.
What is one explanation of how SZ can have a genetic origin in the absence of family history with SZ?
Mutation in parental DNA which can be caused by radiation, position or viral infection.
Where does evidence of mutation come from?
Positive correlations between paternal age and risk of SZ increasing from around 0.7% with fathers under 25 to over 2% in fathers over 50 - Browne et al.
Evaluation of the genetic basis of schizophrenia:
Stregnth = genetic explanations have strong evidence.
-Gottesman shows the risk of SZ increases with genetic similarity to a family member with SZ which means some people are more vulnerable to SZ resulting from genetic make-up.
Evaluation of biological explanations of SZ
Limitation = clear evidence showing environmental factors also increase the risk of SZ
Morkved et al showed that 67% of people with SZ and related psychotic disorders reported at least one trauma as opposed to 38% of a matched group with non-psychotic mental health issues this means genetic factors cant provide a complete explanation.
What is the best known neural correlate for SZ?
Dopamine
What is dopamine important in?
The functioning of several brain systems related to symptoms of SZ.
What was the original dopamine hypothesis based on?
The discovery that’d rugs used to treat SZ caused symptoms similar to those with Parkinson’s disease - Seeman.
Therefore SZ might be the result of high dopamine levels = hyperdopaminergia in subcortical areas of the brain.
Who proposed the addition to the original dopamine hypothesis?
Davis et al
What did Davis et al propose?
Corticol hypodopaminergia = abnormally low dopamine levels in the brains cortex which can explain symptoms of SZ.
What has corticol hypodopaminergia been suggested to lead to?
Subcortical hyperdopaminergia so both high and low levels of dopamine in different brain regions are part of the dopamine hypothesis.
What else does the current version of the dopamine hypothesis try to explain?
The origins of abnormal dopamine functions.
Evaluation of neural correlates of SZ
Strength = support for the idea that dopamine is involved with SZ
Research has shown that amphetamines increase dopamine and worsen symptoms of SZ and induce symptoms in people without SZ whereas antipsychotic drugs reduce dopamine activity and reduce the intensity of SZ symptoms. Also there are some candidate genes which act on the production of dopamine or dopamine receptors which suggests dopamine is involved in symptoms of SZ.
Evaluation of neural correlates of SZ
Limitation = evidence for a central role of glutamate
- Post-mortem and live scanning have found raised levels of glutamate in several brain regions of people with SZ. Also several candidate genes for SZ are believed to be involved in glutamate production or processing.
Which means that a strong case can be made for glutamate and dopamine in their role in SZ.
