Biological Explanations Flashcards
What are 2 biological explanations for schizophrenia? One broken into 3 more explanations
Genetic factors
Neural correlates - dopamine hypothesis, reduced activity in ventral striatum and enlarged ventricles
What are genetic factors?
Inherited factors make certain individuals more likely to develop a behaviour or mental disorder.
What evidence shows supports for genetic influences?
Gottesman (1991)- Carried out a large scale family study to investigate the genetic influence of schizophrenia.
The more genetically similar you are to a family member, the higher the shared risk of schizophrenia.
Identical twins - 48%, Fraternal twins -17%, Nieces and Nephews 4%
What are neural correlates?
Changes in neuronal events and mechanisms that result in the characteristic symptoms of a behaviour or mental disorder.
What is the dopamine hypothesis?
Claims that an excess of the neurotransmitter dopamine in certain regions of the brain is associated with the positive symptoms of schizophrenia and lack of dopamine with negative symptoms.
What is hyperdopaminergia?
Excessive levels of dopamine in the subcortex and Borca’s area leading to positive symptoms
What is hypodopaminergia?
Low levels of dopamine in the prefrontal cortex leading to negative symptoms
Explain the two other changes in the brain linked to symptoms of schizophrenia?
- Reduced activity in the ventral striatum (reward system)- Link found between avolition and ventral striatum. This region in the brain is crucial in the anticipation of reward.
- Enlarged ventricles- linked to negative symptoms. Ventricles are fluid filled cavities that supply nutrients and remove waste. These have found to be 15% bigger in those with schizophrenia.
2 Strengths of genetic explanations for schizophrenia (1 COUNTER)
Evidence for genetic susceptibility:
Gottesman 1991 - twins MZ - 48%, DZ - 17%
COUNTER - Equal environment assumption. MZ twins treated more similarly than DZ twins. Could be environmental differences.
Role of mutation:
Mutation in parental DNA can explain how schizophrenia takes place in absence of family history of the disorder. Brown et al (2002) found a positive correlation between parental age (associated with increased risk of sperm mutation) and risk of schizophrenia increasing from about 0.7% with fathers under 25, to over 2% in fathers over 50. Also highlights the genetic influence on schizophrenia
2 Strengths of neural correlates (2 counter limitations)
Evidence from brain scanning research
Juckel et al. (2006)- measured activity levels in the ventral striatum in schizophrenics and found lower levels of activity than those observed in controls.
COUNTER - Does not show a causal relationships. It may be that the negative symptoms themselves have resulted in less info passing through the ventral striatum resulting in reduced activity, rather than the reduced activity causing the negative symptoms.
Evidence for dopamine hypothesis from drugs:
There has been successful drug treatment for schizophrenics which attempt to change levels of dopamine activity in the brain.
1. Drugs that increase dopaminergic activity: - Amphetamines are dopamine agonists and increase levels of dopamine. ‘Normal’ individuals exposed to amphetamines can develop characteristic symptoms of a schizophrenic episode, which disappear when they stop taking drug.
2. Drugs that decrease dopaminergic activity: - Antipsychotic drugs- block activity of dopamine and so eliminate symptoms such as hallucinations and delusions.
COUNTER - Noll (2009) found that psychotic drugs do not alleviate hallucinations and delusions in about one third of people. In addition, in some people, hallucinations and delusions are present despite levels of dopamine being normal.
