Biological Explanations

Question 1

Biological Explanations

Family Studies

Answer 1

• Family studies have confirmed the risk of schizophrenia is increased if a person has a relative with the disorder.
• The percentage ranges from 2% for aunts and 48% for identical twins.
• Families also share the same environment in addition to their genes, so the increased risk is likely a combination of both.

Question 2

Biological Explanations

Candidate Genes

Answer 2

• Schizophrenia is polygenic meaning there is more than one gene involved in its development.
• Studies identified different candidate genes so it appears schizophrenia is aetiologically heterogenous.
• It’s possible these genes are those that code for dopamine.

Question 3

Biological Explanations

Mutation

Answer 3

• It also seems paternal age can affect the risk of schizophrenia.
• Sperm mutation can occur in old age which increases the risk of schizophrenia from 0.7% in fathers under 25 to 2% in those over 50.

Question 4

Biological Explanations

Dopamine Hypothesis

Answer 4

• Drugs used to treat schizophrenia cause symptoms similar to parkison’s disease (associated with low DA).
• Therefore, schizophrenia may be caused by high levels of DA in subcortical areas of the brian (subcortical hyperdopaminergia).
• A high concentration of DA in Broca’s area can impact speech functon which explains the speech poverty experienced by some people with schizophrenia.
• The hypothesis has been expanded to include hypodopaminergia in the prefontal cortex which could explain some cognitive problems (delusions) with schizophrenia.

Question 5

Biological Explanations: Evaluation

Support from Adoption Studies

Strength

Answer 5

• It seems that genetic explanations for schizophrenia are supported by family studies.
• Research has found that risk increases with genetic similarity to family with schizophrenia.
• Adoption studies show that biological children of parents with schizophrenia are at heightened risk even if they grow up in a different environment.
• Hilker (2018) showed a concordance rate of 33% for MZ twins and 7% for DZ twins.

This suggests that people are more vulnerable to schizophrenia as a result of their genetic make-up.

Question 6

Biological Explanations: Evaluation

Environmental Factors

Limitation

Answer 6

• There is clear evidence that environmental factors affect the risk of schizophrenia.
• Psychological risk factors such as childhood trauma can increase the chance of developing mental disorders, in particular schizophrenia in those with an existing risk.
• 67% of people with schizophrenia reported at least one childhood trauma, opposed to 33% in a control group.

This means that genetic factors alone cannot provide a complete explanation for schizophrenia.

Question 7

Biological Explanations: Evaluation

Evidence for Dopamine

Strength

Answer 7

• There is support for the significance of DA in schizophrenia.
• Ampethamines which increase DA worsen symptoms in people with schizophrenia and induces symptoms in those without.
• Antipyschotic reduce DA levels and reduce the intensity of symptoms.

This strongly suggests that dopamine is involved in the symptoms of schizophrenia.

Question 8

Biological Explanations: Evaluation

Glucamate

Limitation

Answer 8

• The dopamine hypothesis does not consider the central role of the NT glucamate.
• Post-mortem and live scanning techniques have found high levels of glucamate in several brain regions of people with schizophrenia.
• In additon, serveral candidate genes are believed to be involved in glucamate production.

This means an equally strong case can be made for the role of other neurotransmitters such as glucamate.