outline and evaluate biological explanations of schizophrenia (genetics and neural mechanisms)

Question 1

outline genetics

Answer 1

according to the genetic explanations, schizophrenia is hereditary

gene mapping revealed not a single schizophrenia gene but several > polygenic

gottesman (1991) study found MZ twins 48% concordance rate, DZ 17%
- supports genetic explanation as it suggests the more genetically similar you are, the more likely you are to have schizophrenia

Question 2

outline dopamine hypothesis

Answer 2

hyperdopaminergia - excess dopamine levels in subcortical > positive symptoms

e.g. excess of dopamine receptors in Broca’s area associated with experience of auditory hallucinations - original dopamine hypothesis

hypodopaminergia - low levels of dopamine in cerebral cortex > negative symptoms

e.g. low levels of dopamine in pre-frontal cortex associated with negative symptoms - most recent dopamine hypothesis

both abnormally high & low levels of dopamine causes schizophrenia

Question 3

outline one or two neural correlates

Answer 3

lower activity in ventral striatum

VS involved in anticipation of reward
- Jucket et al 2006 found lower levels of activity here compared to healthy control
- loss of motivation may be explained by lower activity levels here

positive symptoms of schizophrenia also have neural correlates
- the temporal gyrus is responsible for processing sounds
- allen et al 2007 found that patients experiencing auditory hallucinations recorded lower activation levels in the temporal gyrus compared to healthy

Question 4

limit 1

Answer 4

of genetic explanations is that MZ twins encounter similar environments

crucial assumption underlying all twin studies is that environment of MZ & DZ twins are equivalent so differences between MZ & DZ can be attributed to genetic factors

joseph 2004 suggested MZ twins encounter more similar environments & experience more ‘identity confusion’

suggests differences in concordance reflects environmental differences

Question 5

strength 1

Answer 5

of dopamine hypothesis is that is has supporting research

curren et al 2004

found that when non-schizophrenics take amphetamins, they start to experience psychotic symptoms

suggests increased levels of dopamine doesn’t correlate with symptoms

Question 6

strength 2

Answer 6

of neural correlates is that they have supporting research

vita et al 2012 performed meta-analysis and found

patients with schizophrenia showed a higher reduction in cortical grey matter volume over time

suggests that decreased levels of grey matter does contribute to schizophrenia, strengthening biological explanations

Question 7

strength 3

Answer 7

neural correlates is that it has implications for treatments

because ‘treatment as prevention’ has begun in some North American longitudinal studies, which use neuroimaging to predict who will develop mental health disorders

e.g. individuals seen to have abnormally lower levels of activity in the ventral striatum and/or superior temporal gyrus could be flagged as ‘at risk patients’

suggests that biological explanations could potentially benefit society as future researchers may be able to treat ‘at risk’ patients before psychosis develops