Biological explanations (SZ) Flashcards
What did Irving Gottesman’s (1991) family study outline the percentages for a person having schizophrenia for a) aunt b) sibling
c) identical twin
a) aunt = 2%
b) sibling = 9%
c) identical twin = 48%
What does polygenic mean and is schizophrenia polygenic?
-Polygenic = when there are many candidate genes implicated in a disorder
- schizophrenia is polygenic
What do the candidate genes of SZ most likely effect?
-Those coding for neurotransmitters, especially dopamine
In Stephen Ripke’s study how many people were studied and how many separate genetic variations were implicated with SZ?
-37,000 people with SZ compared to 113,000 controls
-Found 108 separate genetic variations implicated in SZ
What is aetiologically heterogeneous and is SZ it?
-aetiologically heterogeneous: a number of different genes can lead to SZ
-And yes SZ is aetiologically heterogeneous
What are the chances of sperm mutation from radiation, poison or viral infection, on fathers aged a) 25 b) 50 to increase chances of SZ
a) fathers aged 25+ have 0.7% chance of sperm mutation for SZ
b)Fathees aged 50+ have 2% of sperm mutation for SZ
What is the AO3 for the genetic basis for SZ?
-S: Research support: Tienari et al. (2004) found that biological children of parents with SZ have heightened risk for SZ despite growing up with adopted family. Recent twin study by Hiker (2018) found concordance rate of 38% for SZ for identical twins and 7% for non-identical twins
-L:Environmental factors: Environmental factors also increase the risk for developing SZ. Psychological factors: Morkved (2017) found 67% of people with SZ related psychotic disorders reported atleast 1 childhood trauma incident opposed to 38% of matched group with non-psychotic mental health issues. This means other factors outside genetics.
What are neural correlates?
-Patterns of structures or activity in the brain that correlate/effect the symtpoms of the disease
What neural correlate is involved with SZ?
-Dopamine
What was the original dopamine hypothesis?
-Based on the discovery that anti-psychotics (drugs used to treat SZ) caused symptoms similar to that in Parkinson’s disease ( a condition associated with low levels of dopamine.
-Therefore SZ might be the result of hyperdopaminergia in subcortical areas of the brain. e.g. excess dopamine receptors in Broca’s area could cause speech poverty
What is the updated version of the dopamine hypothesis?
-Davis (1991) proposed hypodopaminergia in cortex: e.g. low levels of dopmaine in prefrontal cortex explain cognitive issues (negative symptoms in SZ)
- Also tries to explain links between levels of dopamine and symptoms: Howes (2017) found early experiences of stress lead to more sensitive to differing levels of dopamine
What is a) hyperdopaminergia and b) hypodopaminergia?
A) hyperdopaminergia : high levels of dopamine
b) hypodopaminergia: low levels of dopamine
what is the AO3 for neural correlates for SZ?
-S: Evidence for dopamine: Curran (2204) found that amphetamines increase dopamine and worsen symptoms in people with SZ and induce symptoms in those who don t. Secondly anti-psychotics lower dopamine and relieve symptoms.
-L: Glutamate: evidence for involvement of glutamate which is ignored in dopamine hypothesis. Post-mortem and live scanning studies found raised levels of glutamate in several brain regions of people with SZ. Additionally, candidate genes for SZ involved with glutamate production. This means other neurotransmitters are involved.
