biological explanations for schizophrenia Flashcards
outline genetic factors
according to the genetic explanation, schizophrenia is hereditary
gene mapping has revealed that there is not a single ‘schizophrenia gene’, but several different genes are involved and increase a person’s vulnerability to developing the disorder, such as the PCM1 gene and NRG3
combination of multiple genes are involved in development of schizophrenia, meaning its polygenic
genes associated with increased risk included those coding for a number of neurotransmitters, including dopamine
supporting evidence for genetic factors
gottesman (1991) study found MZ twins have a 48% shared risk of schizophrenia, whereas DZ twins have a 17% shared risk
this therefore supports genetic explanation because it suggests the more genetically similar you are, the more likely you are to have schizophrenia
adoption studies
Tiernari et al (2000) found that 164 adoptees whose biological mothers had been diagnosed with schizophrenia, 11 (6.7%) also received a diagnosis of schizophrenia, compared to 4 (2%) of the 197 control adoptees (those born to non-schizophrenic mothers)
suggests that, even when the environmental influence of the biological mother was removed, the genetic risk was still evident
limit of genetic explanations
can be considered biologically reductionist
when a study reduces the behaviour down to biological components, ignoring other factors
e.g. Genain (2001) found that MZ twins who have experienced greater stress (e.g. abuse) developed schizophrenia quicker and showed more severe symptoms than those who experienced less stress
suggests development of schizophrenia is explained by both environmental and biological factors, and a more holistic explanation would be best
dopamine hypothesis
dopamine appears to work differently in brain of a patient suffering from schizophrenia
both abnormally high and low levels of dopamine cause schizophrenia
original dopamine hypothesis
suggests there were excess dopamine levels in subcortical (inner layers) areas of the brain, which caused the positive symptoms of schizophrenia
e.g. excess of dopamine receptors in Broca’s area has been associated with experience of auditory hallucinations
hyperdopaminergia
more recent dopamine hypothesis
suggests that there are low levels of dopamine within the brains cerebral cortex (outer layer), which causes the negative symptoms of schizophrenia
e.g. low levels of dopamine in the pre-frontal cortex (responsible for decision-making) has been associated with negative symptoms of schizophrenia
hypodopaminergia
dopamine strength
supporting research evidence
curren (2004)
found that when non-schizophrenics take amphetamines (which increase dopamine levels in the brain) they start to experience psychotic symptoms (e.g. delusions and hallucinations)
suggests increased levels of dopamine in the brain does correlate with schizophrenic symptoms, like the original dopamine hypothesis suggests
loss of grey matter and enlarged ventricles
ventricles are fluid filled spaces in the brain, which are responsible for removing waste and protecting the brain
enlarged ventricles are correlated with the development of schizophrenia, specifically the negative symptoms
enlarged ventricles in schizophrenic patients is suggested to be a result from the loss of grey matter
Andreason compared the ventricle size of schizophrenics and non-schizophrenics under the age of 50 using MRI scans and found that schizophrenics showed a mean increase in ventricle of 20%
negative symptoms - lower levels of activity in the ventral striatum
the ventral striatum is involved in the anticipation of reward (related to motivation)
Juckel et al (2006) found lower levels of activity in the VS compared to a healthy control
loss of motivation (avolition) in schizophrenia may be explained by lower activity levels here
positive symptoms - lower levels of activity in the superior temporal gyrus
positive symptoms of schizophrenia also have neural correlates
temporal gyrus is responsible for processing sounds
allen et al (2007) found that patients experiencing auditory hallucinations recorded lower activation levels in the superior temporal gyrus compared to a healthy control
strength of neural explanations
supporting research evidence
vita et al (2012) performed a meta analysis and found
patients with schizophrenia (compared to a healthy control) showed a higher reduction in cortical grey matter volume over time
suggests that decreased levels of grey matter does contribute to schizophrenia, strengthening the biological explanations
limit of neural explanations
there are cause and effect issues
which is when a method does not allow a causal relationship to be established between the IV and DV, decreasing internal validity
e.g. we cannot be sure whether enlarged ventricles is causing schizophrenia, or whether enlarged ventricles is a result of schizophrenia
suggests that it is hard to make concrete conclusions about the causes of schizophrenia when using neural explanations, weakening its usefulness
implications for treatment
strength of neural
strength of neural correlates for schizophrenia is that it has implications for treatment
this is because ‘treatment as prevention’ has begun in some north american longitudinal studies, which use neuroimaging to predict who will develop mental health disorders, such as schizophrenia
e.g. individuals who are seen to have abnormally lower levels of activity in the ventral striatum and/or the superior temporal gyrus could be flagged up as ‘at risk patients’
this suggests that the biological explanations of schizophrenia could potentially benefit society, as future researchers may be able to treat ‘at risk’ patients before psychosis develops
