Biological Explanations For Schizophrenia

Question 1

Genetic Basis: What have family studies shown about schizophrenia?

Answer 1

• the risk of schizophrenia increases in line with genetic similarity to a relative with the condition.

Question 2

Genetic Basis: Who investigated genetic similarity and schizophrenia and how?

Answer 2

• Gottesman: Large-scale family study.
• Someone with an aunt with schizophrenia has a 2% of developing it.
• 9% if their sibling has it.
• 48% if they are an identical twin.

Question 3

Genetic Basis: What do family members tend to share which may also affect the development of schizophrenia?

Answer 3

• their environment

Question 4

Genetic Basis: What did early research into candidate genes and their effect on schizophrenia look for?

Answer 4

• a single genetic variation in the belief that one faulty gene could explain schizophrenia.

Question 5

Genetic Basis: What does it mean that schizophrenia is polygenic?

Answer 5

• there are a number of different genes involves with the onset of schizophrenia.

Question 6

Genetic Basis: How did Ripke investigate the role of candidate genes on schizophrenia?

Answer 6

• Combined all previous data from genome-wide studies of schizophrenia.
• The genetic makeup of 37,000 people with a diagnosis of schizophrenia was compared to 113,000 controls.
• 108 separate genetic variations were associated with slightly creased risk of schizophrenia.

Question 7

Genetic Basis: What does it mean that schizophrenia is aetiologically heterogenous?

Answer 7

• different combination of factors, including genetic variation, can lead to the condition.

Question 8

Genetic Basis: How may schizophrenia have a genetic origin even in the absence of a family history of the disorder?

Answer 8

• mutation in parental DNA which can be caused by radiation, poison or viral infection.

Question 9

Genetic Basis: What has research shown about the effect of mutation on schizophrenia?

Answer 9

• positive correlations between paternal age and risk of schizophrenia, increasing from around 0.7% with fathers under 25 to 2% in fathers over 50.

Question 10

Neural Correlates: What was the original dopamine hypothesis based on?

Answer 10

• the discovery that drugs used to treat schizophrenia (antipsychotics which reduce dopamine) caused symptoms similar to those in people with Parkinson’s disease, a condition associated with low dopamine levels.

Question 11

Neural Correlates: What did the original dopamine hypothesis believe that schizophrenia may be the result of?

Answer 11

-high levels of dopamine in subcortical areas of the brain.

Question 12

Neural Correlates: How may the original dopamine hypothesis explain the speech poverty or auditory hallucinations symptoms of schizophrenia?

Answer 12

• an excess of dopamine receptors in pathways from the subcortex to Broca’s area may explain speech poverty or auditory hallucinations.

Question 13

Neural Correlates: How has the original dopamine hypothesis been revised?

Answer 13

• Davies proposed the addition of cortical hypodopaminergia (abnormally low dopamine in the brains cortex).

Question 14

Neural Correlates: What may low dopamine in the prefrontal cortex explain?

Answer 14

• cognitive problems (negative symptoms of schizophrenia)

Question 15

Neural Correlates: What has cortical hypodomaminergia been suggested to lead to and what does this mean?

Answer 15

• subcortical hyperdopaminergia, so both high and low levels of dopamine are involved in the revised model.

Question 16

Evaluation: Research Support - Genetic Basis

Answer 16

• Strength = Strong evidence base
• Gottesman study shows that the risk increases with genetic similarity to a family member with schizophrenia.
• Adoption studies such as Tienari et al show that biological children of parents with schizophrenia are at heightened risk even if they grow up in an adoptive family.
• Hilker’s twin-study showed a concordance rate of 33% for identical twins and 7% for non-identical twins.
• Shows that some people are more vulnerable to schizophrenia as a result of their genetic makeup.

Question 17

Evaluation: Environmental Factors - Genetic Explanation

Answer 17

• Limitation = Clear evidence to show that environmental factors also increase the risk of developing schizophrenia.
• Environmental factors include both biological and psychological influences.
• Biological Influences: Birth complications and smoking THC- rich cannabis in teenage years.
• Psychological risk factors: Childhood trauma which leaves people more vulnerable to adult mental health problems in general but there is now a particular link with schizophrenia.
• Morkved et al: 67% of people with schizophrenia and related psychotic conditions reported at least one childhood trauma, compared to 38% of a matched group with non-psychotic mental health problems.
• Genetic factors alone cannot provide a complete explanation for schizophrenia.

Question 18

Evaluation: Glutamate - Neural Basis

Answer 18

• Limitation of the dopamine hypothesis = evidence for the central role of glutamate.
• Post-mortem and live scanning studies have consistently found raised levels of the neurotransmitter glutamate in several brain regions of people with schizophrenia.
• In addition, several candidate genes for schizophrenia are thought to to be involved in glutamate production or processing.
• Equally strong case can be made for a role for other neurotransmitters.