Biological explanations of SZ

Question 1

Biological explanations of SZ

Answer 1

based on 2 factors:
- genetic basis
- neural correlates including the dopamine hypothesis

Question 2

genetic basis

Answer 2

normally tested through:
- family
- twin
- adoption studies

Question 3

family studies - genetic basis

Answer 3

• find individuals who have SZ + determine whether their biological relatives are similarly affected more often than non-biological relatives
• Gottesman (1991) found that if both parents were SZ, the likelihood of the offspring also having SZ was 46%
• if only one parent, likelihood dropped to 13%
• if a sibling, likelihood was 9%

= the closer you are genetically related, more likely to get SZ

Question 4

twin studies - genetic basis

Answer 4

As MZ twins share 100% of their genes, whereas DZ share 50% (me and tanz)
= if SZ is genetic, then concordance rates should be higher for MZ than DZ twins
- Gottesman found 48% concordance rate for MZ and 17% for DZ
= more genetically similar you are then the more likely you are to get SZ

Question 5

adoption studies - genetic basis

Answer 5

adoption studies carried out to understand the influence of nature + nurture

= a study carried out in Finland, found that 164 adoptees who biological mothers had SZ, 11(6.7%) were also diagnosed w/ SZ - compared to control group of 197 adoptees where only 4 (2%) were diagnosed w/ SZ

= shows that overall %age of children (who’ve been adopted by non-SZ parents) having SZ was very low

Question 6

candidate genes

Answer 6

SZ is polygenic = there is a combination of different genes that have been implicated in SZ

• study compared the genetic makeup of 37000 SZ patients worldwide + found that 108 separate genetic variations were associated with an increased risk of SZ

= the genes that were particularly vulnerable were the ones associated to the functioning of certain neurotransmitters e.g. dopamine

Question 7

ads of genetic basis of SZ

Answer 7

there is a wealth of research evidence to support the genetic basis for SZ, shown through Gottessman, Joseph’s + Tienari’s study:
- there is a link between genes + SZ
- this is a strength cus if a child grows up in a family where both their bio parents has SZ, then the chances of them getting SZ is heightened compared to only one/ none of the parents having it
= genetics is an important factor

Question 8

disads of genetic basis of SZ

Answer 8

• separating nature + nurture
• DNA mutation
• diathesis stress model

Question 9

separating nature + nurture - disads of genetic basis of SZ

Answer 9

difficult to separate nature (genes) from nurture (environment)
= look at adoption studies that attempt separate genes from the environment, children are raised by relatives in a similar way to biological parents
= adoption studies may not always be a good comparison for the effects of nature + nurture

Question 10

DNA mutation - disads of genetic basis of SZ

Answer 10

SZ can take place in the absence of a family history
- may be a mutation in parental DNA
= supported by study where a positive correlation was found between paternal age + increased risk of SZ
- from around 0.7% w/ fathers under 25 to over 2% w/ fathers over 50
- no direct genes are involved, but a person can still get SZ if their father was older at the time of fertilisation

Question 11

diathesis stress model - disads of genetic basis of SZ

Answer 11

the diathesis stress model suggests that there is a genetic vulnerability in SZ
= this vulnerability is only triggered if there is a stress-trigger - if your life is stress-free then you may not end up having the disorder
= thus we need to be cautious when looking at genetic factors since they alone may not trigger SZ

Question 12

the dopamine hypothesis - neural correlates

Answer 12

• neurotransmitters are the brains chemical messengers
• claims that an excess of the neurotransmitter dopamine in certain regions of the brain is associated with +ve symptoms fo SZ
• the messages from neurons that transmit dopamine fire too easily + too often (more dopamine binding + neurons firing)
  = leading to hallucinations/ delusions

Question 13

two consequences of the dopamine hypothesis

Answer 13

• hyperdopaminergia
• hypodopaminergia

Question 14

hyperdopaminergia

Answer 14

• consequence of the dopamine hypothesis
• when there are high levels of dopamine which link to positive symptoms of SZ

Question 15

hypodopaminergia

Answer 15

• consequence of the dopamine hypothesis
• when there are low levels of dopamine which link to negative symptoms

Question 16

ads of the dopamine hypothesis

Answer 16

• supporting research
• antispychotic antagonist drugs

Question 17

disads of the dopamine hypothesis

Answer 17

• other factors involved
• correlation-causation problem

Question 18

supporting research - ads of the dopamine hypothesis

Answer 18

there is drug research to support the dopamine hypothesis
= dopamine agonists tend to increase dopamine levels + make the SZ symptoms worse, supporting the idea of hyperdopaminergia

Question 19

antipsychotic antagonist drugs - ads of the dopamine hypothesis

Answer 19

antipsychotic drugs act as antagonists to reduce the levels of dopamine (help control symptoms)
= supports the idea that dopamine levels are high in SZ + can be reduced through drugs

Question 20

other factors involved - disads of the dopamine hypothesis

Answer 20

the dopamine hypothesis cannot be seen as the sole cause of the SZ as there are other biological + psychological factors that contribute e.g. upbringing of family dysfunction or cognitive explanations
- also more research has found that dopamine may not be the only neurotransmitter responsible for SZ, research conducted on glutamate + seretonin

Question 21

correlation-causation problem - disads of the dopamine hypothesis

Answer 21

we don’t know whether the individual started having excess levels of dopamine + started experiencing symptoms of SZ OR did the individual first experience symptoms of SZ and consequently have high levels of dopamine?
= doesn’t explain cause + effect