Biological And psychological Flashcards
Genetic basis of SZ
- SZ runs in famailies
- Strong relationship between genetic similarity and likelihood of developing SZ
- 48% identical twins
- 17% non-identical
Candidate genes
- Appears to be aetiologically heterogenous (different combos lead to SZ)
- Genes include those that code for a number of neurotransmitters
- Ripke
Describe Ripkes study into candidate genes
- Genome wide study
- Genetic make up of 37,000 patients compared with 113,000 controls
- 108 genes associated with SZ
Dopamine hypothesis
Dopamine Systems seem to be faulty
What is the original hypothesis
- Hyperdopaminergia in the sub cortex
- Possible high levels of dopamine
- Such as high numbers of dopamine receptors in Broca’s area may be associated with speech poverty
What is the updated hypothesis
- Hypodopaminergia in the cortex
- Low levels of domapine identified in the prefrontal cortex (decision making) could cause the negative symptoms
- Could be that both are correct
Neural correlates
These are measurements of structure and function of the brain that correlate with experience
Neural correlates of negative
- Avolition is loss of motivation
- Ventral striatum inloved In reward system
- Lower levels of activity in striatum in SZ than in controls
- Moreover a negative correlation between levels of activity and severity of overall negative symptoms
Neural correlates of positive symptoms
- Brain scans of those who experience auditory hallucinations and compared to control
- Had to identify pre-recorded speech as their own of others
- Lower activity in the superior temporal gyrus were found in hallucination group
Multiple sources of evidence for genetic susceptibility
- Gottesman: showed relationship between shared genes and genetic vulnerability
- Adoption studies
- Ripke et al into candidate genes
- All these studies genetic susceptibility is important
Describe the concordance rates in Gottesmans study
Identical: 48%, 100% genes
Non-identical: 17%, 50% genes
Children: 13%
evidence for dopamine hypothesis
- Inflammatory response
- Dopamine agonists such as amphetimans can produce SZ like symptoms
- Antipsychotics work by reducing dopamine
- Radioactive tags on chemicals needed to make dopamine taken up faster than in controls
Evidence against dopamine hypothesis
- Some genes identified don’t code for dopamine
- New focus on glutamate neurotransmitter
- So there is mixed evidence for hypothesis
Correlation-causation problem
- Number of neural correlates for SZ
- Is it these areas cause the symptoms or is there a 3rd factor that causes both
- For instance reduced activity in striatum may inhibit it’s development
What are the 3 family dysfunction explanations
- Schizophrenigenic mother
- Double-bind
- Expressed emotion