Biological Explanations of Schizophrenia Flashcards
Define polygenic.
The idea that numerous genes are involved in causing schizophrenia.
Outline the genetic basis of schizophrenia.
A faulty candidate gene is inherited from the patient’s parents, causing them to acquire schizophrenia as a result.
Give an example of the genetic basis of schizophrenia.
The COMT gene, which breaks down dopamine, may be ineffective at doing so. Resulting in a higher concentration of dopamine which is linked to hallucinations.
Give supporting twin study evidence for the role of genetic in schizophrenia.
Gottesman and Shields found a concordance rate of 48% for monozygotic twins and 17% for dizygotic twins.
Give an advantage of the genetic basis of schizophrenia.
Advantages:
- Much supporting twin study evidence - e.g. Joseph - compiled all date from prior 2001 and found a concordance rate of 40% for MZ and 7% for DZ twins.
- Supporting evidence from adoption studies -Tienari et al. - adoptees required the genetic predisposition to SZ to develop it - family dysfunction was insufficient on its own.
Give a disadvantage of the genetic basis of schizophrenia.
Disadvantages:
- Findings from twin studies do not demonstrate true causation - a purely genetic cause would give rates of 100% - there is another factor that causes SZ.
- Twin studies take place in the same family environment - may be difficult to disentangle the true cause, whether genetic or environmental - does not answer the Nature v. Nurture debate.
- Biologically deterministic - ignores many possible causes - free will means potential patients may avoid environmental stimuli and begin therapy in the early onset of SZ.
What does the dopamine hypothesis state causes schizophrenia?
- An abnormally high number of D2 receptors on the postsynaptic neurones.
- Causes an increase in dopamine levels.
- Increased neuron firing due to excitatory nature.
- E.g. in Broca’s area may cause speech poverty.
Give some advantages of the dopamine hypothesis.
Advantages:
- Supporting evidence - e.g. Thornley at al. - 13 drug trials - chlorpromazine was associated with a reduction in SZ symptoms - this drug reduces dopamine levels.
- Pharmacological applications - led to the creation of antagonistic drugs - allows patient to enjoy a better quality of life - whilst being relatively inexpensive.
Give two disadvantages of the dopamine hypothesis.
Disadvantages:
- Inconclusive and contradictory evidence - Noll - only help to reduce symptoms in 1/3 of cases - individuals may experience symptoms with low dopamine levels suggesting dopamine is one of many causal factors.
- Too biologically reductionist - many other potentially contributing neurotransmitters in SZ e.g. glutamate - also psychological factors may influence, and cause, SZ.
What does the neural correlates theory suggest causes schizophrenia?
A reduced density of neurons in the superior temporal gyrus results in auditory hallucinations.
What is the consequence of enlarged ventricles in relation to schizophrenia?
Enlarged ventricles in the central brain areas and prefrontal cortex have been linked to negative symptoms of SZ such as disorganised thinking and avolition.
Give two advantage of the neural correlates theory.
Advantages:
- Supporting evidence for the density of grey matter - Milev et al. - 5 year longitudinal study of 123 patients - smaller temporal lobe grey matter negatively correlates with persistence of hallucinations.
- Supporting evidence for role of enlarged ventricles in SZ - Ho et al. - 73 patients with 23 controls - enlargement in frontal lobe fluid volume negatively correlated with the severity of disorganise thinking - disorganised thinking has a neurological basis.
- Research uses empirical methodology - MRI and PET scans are used - replicable (highly reliable) and free from potential biases - though could be said to be reductionist when used in isolation.
Give two disadvantages of the neural correlates theory of schizophrenia.
Disadvantages:
- Correlational findings - no causation - does not show whether structural anomalies in the brain are the cause of schizophrenia - e.g. reduced activity in the ventral striatum may negative symptoms or the negative symptoms may cause reduced activity in the ventral striatum.
