SZ: Biological Explanations

Question 1

Biological explanations

Answer 1

Emphasise role of inherited factors and dysfunction of brain activity in development of a mental disorder.

Question 2

Dopamine hypothesis

Answer 2

Claims an excess of neurotransmitter dopamine in certain brain regions is associated with positive symptoms of SZ.

Question 3

Genetics

Answer 3

Inherited factors make certain individuals more likely to develop behaviours or mental disorder.

Question 4

Neural correlates

Answer 4

Changes in enuronal events and mechanisms that result in the characteristic symptoms of a mental disorder.

Question 5

List the studies that demonstrate the impact of genetic factors in SZ:

Answer 5

• Family studies - Gottesman, 1991
• Twin studies - Joseph, 2004
• Adoption studies - Tienari, 2000

Question 6

Overall, what have family studies of SZ found?

Answer 6

SZ is more common among biological relatives of a person with SZ, and that the closer the degree of genetic relatedness, the greater the risk.

Question 7

What were the results of Gottesman’s family studies of SZ?

Answer 7

• 2 SZ parents - concordance rate = 46%
• 1 SZ parent - concordance rate = 13%
• SZ sibling - concordance rate = 9%

Question 8

MZ twins

Answer 8

Monozygotic twins - genetically identical

Question 9

DZ twins

Answer 9

Dizygotic twins - only share 50% of genes.

Question 10

If MZ twins are more concordant than DZ twins, what does this suggest?

Answer 10

That the greater similarity is due to genetic factors.

Question 11

What were the results of Joseph’s twin studies of SZ?

What did later studies suggest?

Answer 11

• MZ concordance rate = 40.4%
• DZ concordance rate = 7.4%

More recent studies (blind diagnosis - not known if twin is MZ or DZ) reported lower concordance rate for MZ twins - but still support genetic position, as still many times higher than DZ twins.

Question 12

Why are adoption studies often used?

Answer 12

As it is often difficult to separate genetic and environmental influences for individuals who share genes and environments.

Question 13

What were the results of Tienari’s adoption studies of SZ?

Answer 13

• SZ mothers = 6.7% children also got diagnosis.
• Non-SZ mothers = 2% children also got diagnosis.

Researchers thought this showed the genetic liability to SZ.

Question 14

Who used family studies to investigate the biological explanations for SZ?

Answer 14

Gottesman, 1991

Question 15

Who used twin studies to investigate the biological explanations for SZ?

Answer 15

Joseph, 2004

Question 16

Who used adoption studies to determine the biological explanations for SZ?

Answer 16

Tienari, 2000.

Question 17

What levels of D2 receptors are SZ thought to have?

Answer 17

Abnormally high levels on receiving neurons, resulting in more dopamine binding and more neurons firing.

Question 18

WIth reference to dopamine, what causes positive symptoms in SZ?

Answer 18

Messages from neurons that transmit dopamine fire too easily or too often, leading to hallucinations and delusions.

Question 19

What is the evidence to support the role played by dopamine in SZ?

Answer 19

• Drugs that increase dopaminergic activity - amphetamines.
• Drugs that decrease dopaminergic activity - antipsychotics.

Question 20

What is amphetamine?

Answer 20

A dopamine agonist - it stimulates nerve cells containing dopamine, causing the synapse to flood with it.

Question 21

How do the effects of amphetamines support the role played by dopamine in SZ?

Answer 21

Individuals exposed to large does of the drug can develop hallucinations and delusions.

Generally this disappears after abstinence from the drug.

Question 22

What did Grilly (2002) discover about dopamine levels and Parkinson’s patients?

Answer 22

Those sufferers that take drugs to higher dopamine levels were found to develop SZ - type symptoms.

Question 23

What do all antipsychotic drugs have in common?

Answer 23

Block the activity of dopamine in the brain - dopamine antagonists.

Question 24

How have antipsychotics shown the role played by dopamine in SZ?

Answer 24

• Drugs that reduce dopamine activities in neural pathways eliminated symptoms like hallucinations and delusions.

Question 25

Describe the revised dopamine hypothesis:

Answer 25

• Positive symptoms are caused by an excess of dopamine in subcortical areas, like the mesolimbic pathway.
• Negative and cognitive symptoms are caused by a deficit of dopamine in prefrontal cortex, like the mesocortical pathway.

Question 26

Who came up with the revised dopamine hypothesis?

Answer 26

Davis and Kahn

Question 27

What research support is their for the revised dopamine hypothesis?

Answer 27

• Neural imaging
• Animal studies

Question 28

How has neural imaging supported the revised dopamine hypothesis?

Answer 28

Patel 2010

• PET scans assessed dopamine levels in SZ and normal individuals.
• Lower levels of dopamine found in dorsolateral PFC of SZ compared to controls.

Question 29

How have animal studies supported the revised dopamine hypothesis?

Answer 29

Wang and Deutch (2008)

• Induced dopamine depletion in PFC of rats.
• Resulted in cognitive impairment which could be reversed using an antipsychotic drug.

Question 30

What are the evaulation points for the genetic factors of SZ?

Answer 30

• Common rearing patterns may explain family similarities.
• MZ twins encounter more similar environments.

Question 31

Write a PEEL paragraph discussing how common rearing patterns may explain family similarities:

Answer 31

P - Research showed SZ appears to run in families.

E - However, many researchers now accept that this might have more to do with childrearing patterns than genetics.

E - Eg. Research on expressed emotion has shown that the negative emotional climate in some families may lead to stress beyond what an individual can cope with, thus triggering a SZ episode.

L - Biological explanations may be overly determinist.

Question 32

Write a PEEL paragraph discussing how MZ twins encounter more similar environments:

Answer 32

P - Assumption of twin studies is that environments of MZ and DZ twins are equivalent.

E - So, assumed that greater concordance for SZ between MZ twins is a result of greater genetic similarity, not the environment.

E - Joseph 2004 pointed out that MZ twins are treated more similarly, experience more similar environments and more identity confusion than DZ twins.

L - Argued that differences in concordance rates between MZ and DZ twins might not reflect genetic differences but rather environmental differences - confounding variable.

Question 33

What are the evaluation poitns for the dopamine hypothesis?

Answer 33

• Evidence from treatment.
• Challenges to hypothesis and inconclusive supporting evidence.

Question 34

Write a PEEL paragraph discussing the evidence for the dopamine hypothesis from treatment:

Answer 34

P - Much of the evidence for the hypothesis comes from successful drug treatments that change the levels of dopamine activity in the brain.

E - Leucht (2013) meta-analysis analysed the effectiveness of different antipsychotic drugs compared to a placebo.

E - All the drugs tested were significantly more effective than placebo in the treatment of positive and negative symproms, acheived through the normalisation of dopamine.

L - Supports the dopamine hypothesis - internal and ecological validity.

Question 35

Write a PEEl paragraph discussing the challenges to the dopamine hypothesis:

Answer 35

P - Inconclusive supporting evidence - Moncrieff

E - Stimulants, like amphetamines, affect many neurotransmitters other than dopamine. Likewise, evidence for dopamine concentrations in post-mortems have been negative or inconclusive.

E - Argues that other confounding sources of dopamine release, eg stress and smoking, have rarely been considered.

L - Suggest dopamine hypothesis is reductionist.