Biological Explanations Flashcards
How do family studies provide support for SZPN
= risk of SZPN increases in line with genetic similarity to relative with disorder
Gottesman 1991 large-scale family study found:
- Aunt with SZPN = 2% chance of development
Vs. Identical Twin = 48% chance of development
What are candidate genes, how do they support SZPN
= genes suspected to be related to disorder based on function/location
- Diff studies identified diff candidate genes (108 seperate genetic variations)
- SZPN = polygenic condition & aetiologically heterogeneous
Define aetiologically heterogenous
= different combinations of genes are implicated in the disorder
What is the role of mutation in SZPN
= SZPN can be caused by mutation in parental DNA
Brown et al (2002)
= found positive correlations between paternal age (associated with greater risk of sperm mutation) and risk of SZPN
- Increases from roughly 0.7% in fathers under 25, & over 2% in fathers over 50
What are neural correlates
Brain structure/activity patterns that occur in conjunction with an experience, may be implicated in origins of that experience
Link DA hypothesis to symptoms of Schizophrenia
`subcortical hyperdominergia
= e.g., excess DA receptors in pathways from subcortex to Broca’s Area, may explain SZPN symptoms of speech poverty/auditory hallucination
cortical hypodominergia
= e.g., low DA levels in prefrontal cortex (responsible for thinking) can explain cognitive problems, i.e. avolition
What is the updated DA hypothesis
Davis et al. proposed that SZPN is caused by subcortical hyperdominergia AND cortical dominergia
Aims to offer explanation for origin of abnormal DA levels
= due to genetic variations and early experiences of psychological/physical stress = increase sensitivity to cortical hypodominergia and subcortical hyperdominergia (Dowes et al)
strength of genetic basis explanation of SZPN
PROS
RESEARCH SUPPORT
= supported by Gottesman family studies, Tieneri at al adoption study (biological children of parents with SZPN = heightened risk even if not brought up by them), concordance studies = higher rates for MZ twins
= supports familial vunerability
weakness of genetic basis explanation of SZPN
CONS
ENVIRONMENTAL FACTORS
= clear evidence of environmental risk factors
e.g. biological (like birth complications, smoking THC-rich cannabis in teens), psychological (childhood trauma)
= genetics not complete explanation on its own
strength of neural correlates explanation of SZPN
PROS
EVIDENCE FOR DA
= support for involvement in SZPN
1. Curran et al
- amphetamines increase DA & worsen symptoms, induce symptoms without
2. Tauscher et al
- antipsychotic drugs reduce DA & intensity of symptoms
3. Evidence of some candidate genes acting on production of DA/DA receptors
weakness of neural correlates explanation of SZPN
CONS
GLUTAMATE
= evidence for central role
1. McCutcheon
- Raised levels of glutamate in several brain regions consistently found in post-mortem/live scanning studies of SZPN ppl
2. several candidate genes believed to be involved in glutamate production/processing
= equally strong case can be made for role of other neurotransmitters
Economic implications of genetic explanation
Practical application
- knowing of genetic link = allows for early intervention, e.g., if SZPNic mother has a child
Genetics = give predisposition to development
Use of interventions to try manage child’s environment so SZPN not triggered
= potentially reduce sufferers of SZPN = less spending on SZPN treatment for NHS
