Biological Explanations Flashcards
(23 cards)
why is it difficult to untangle the genetic contributions to SZ
- there is evidence that SZ runs in families. but families that share the same environment
- strong relationship between the genetic similarity of family members and the likelihood of both developing SZ
is SZ an inherited disorder
people DO NOT inherit SZ
- but do inherit a genetic predisposition to it
Gottesmen 1991 carried out a family study and found the following concordance rates for SZ
- MZ twin: 48%
- DZ twins: 17%
- Siblings: 9%
what do Gottesmen’s findings show
that the closer the degree of genetic relatedness, the greater the risk of developing SZ
what does it mean to say that SZ is polygenic
- SZ might run in the family but no single gene is thought to be responsible.
- polygenic meaning many genes are involved and a polygenic risk factor is calculated
what is the role of genetics in the aetiology of SZ
- different combinations of these genes can lead to SZ.
- therefore it is aetiologically (caused) heterogenous (by different things)
what were the findings of Ripke et al 2014
studied 37,000 patients and found 108 separate genetic variations associated with increased risk of SZ
why are adoption studies helpful in determining the aetiological role of genetics
- a limitation with twin studies is that MZ twins have 100% same DNA they also share an environment
- adoption studies allow for disentangling shared genes from the same environment
what were the findings of Tienari 2000
- of the 164 adoptees whose biological mothers had SZ, 6.7% also were diagnosed compared to 2% of the 197 control group (no SZ mother)
- this is support for a genetic explanation for SZ, but only that it increases the likelihood of developing SZ
what is the dopamine hypothesis of SZ
- dopamine is a neurotransmitter
- the original dopamine hypothesis stated that SZ was caused by excessive activity of dopamine in the subcortex
- causes the neurons responding to dopamine fire too often and transmit too many messages
- message ‘overload’ may produce many symptoms
what is hyperdopaminergia, in where is thought to occur in the brain in patients with SZ
- high levels of dopamine in subcortical areas projecting to Broc’s area may be associated with the experience of auditory hallucinations and/or speech poverty
- it is now thought people with SZ have high numbers of D2 receptors
what is an alternative explanation that would cause excessive dopaminergic activity
it may be that both hyperdopaminergia and hypodopaminergia are correct explanations - both high and low levels of dopamine in different brain regions are involved in SZ
- more recent version focuses on abnormal dompamine systems in the cortex
how does Goldman-Rakic’s 2004 work revise the dopamine hypothesis
- identified low levels of dopamine in the prefrontal cortex in the negative symptoms of SZ such as avolition
- the prefrontal cortex is responsible forthinking and decision making
what does the ‘neural correlates’ of something mean
refers to the measurements of the structure of function of the brain that correlate with an experience.
- both positive and negative symptoms have neural correlates
give an example of the neural correlates of SZ
- proposes that SZ is caused by enlarged ventricles
describe how the stidy by Juckel et al 2006 on the neural correlates of negative symptoms
- found negative correlation between ventral striatum activity and overall negative symptoms of SZ
- loss of motivation may be explained by low level activity in this part of the brain
describe the work by Allen et al. 2007 on the neural correlates of hallucinations
- The superior temporal gyrus consists of the auditory cortex
- found that patients experiencing auditory hallucinations recorded lower activation levels in the superior temporal gyrus and anterior cingulate gyrus
in what regard is research into the biological basis of SZ socially sensitive
- thought to make patients appear less accountable for their disorders, which could increase clinician’s empathy
- suggested that biological accounts of psychopathology can exacerbate perceptions of patients as abnormal, distinct from the rest of the population, meriting social exclusion, and even less than fully human
-ongoing shift toward biomedical conceptualisations has many benefits, Lebowitz et al’s (2014) results reveal unintended negative consequences.
how might a biological explanation of SZ be seen as reductionist
- the effective use of drug treatment increases support for biological explanations of SZ
PEEL - A problem with the genetic argument is that it is difficult to separate the impact of nature and nurture
p - difficult to separate the impact of nature and nurture
e - both family and twin studies investigate individuals who are sharing the same environment, which could be increasing the concordance rates, irrespective of the genes
e - high concordance rates between MZ twins is actually due to them being treated more similarly than DZ twins or ordinary siblings and not in fact due to their genetics
l - could be a confounding variable
PEEL - a strength with the genetic argument is that there is very strong evidence from multiple sources
p - strong evidence from multiple sources
e - Gottesman (1991) Tienari et al (2004)
e - overwhelming evidence to support that genetics makes people more susceptible to developing SZ
l - It may be that genetics are not the only factor in the development of SZ but it does suggest a genetic vulnerability
PEEL - A limitation with the dopamine hypothesis explanation of sz is there is mixed evidence
p - there is mixed evidence
e - amphetamines increase levels of dopamine and can make sz worse & antipsychotic drugs reduce levels of dopamine and can reduce symptoms in sufferers. BUT Ripke suggests other significant neurotransmitters other than dopamine that play a role
e - research has shifted and is investigating the role of the neurotransmitter glutamate
l - does not offer a complete explanation
PEEL - what are limitations of studies in which the neural correlates of symptoms are identified
p - results are only correlational
e - may be that lower ventral striatum activity may cause negative symptoms of SZ such as avolition
e - difficult to use this correlational evidence to imply causation because there may be other intervening factors such as the environment that causes this effect
l - neural correlates is valid argument
