biological explanations for Sz

Question 1

what did Gottesman find about the relationship between genes and Sz

Answer 1

Sz is partly genetic, with ~50% concordance rates for genetically identical twins, with a positive correlation between the % of genes shared and the risk of developing Sz

Question 2

what did Ripke do with candidate genes

Answer 2

combined research of genome-wide studies. he compared the genetic makeup of 37,000 with Sz to 113,000 controls without Sz (total of 150,000)

Question 3

what did Ripke find

Answer 3

108 separate genes associated with a slightly increased risk of Sz

Question 4

how is Sz attributed genetically

Answer 4

Polygenic

Question 5

how can Sz occur in the absence of a family history of the disorder

Answer 5

Mutation in parental DNA, can be caused by radiation, poison, or viral infection.
seen by a positive correlation between paternal age (risk of sperm mutation) and risk of Sz, increasing from ~0.7% with fathers aged <25 to >2% in fathers aged >50

Question 6

what’re 3 strengths of the genetic explanation for Sz

Answer 6

adoption studies
concordance rates in twin studies
genetic counselling

Question 7

how are adoption studies a strength for genetic explanations for Sz

Answer 7

Tienari et al. found adopted children with biological mothers who had Sz were more likely than controls to develop Sz, even with non-Sz adopted parents

Question 8

how are concordance rates from twin studies a strength of the genetic explanation for Sz

Answer 8

Hilker et al found concordance rates for Sz of 33% in MZ and 7% for DZ twins.
this shows that Sz does have genetic basis but with relatively low concordance rates

Question 9

how is genetic counselling a support of genetic explanations for Sz

Answer 9

if parents have Sz, it increases the risk of development for their offspring. research has led to genetic counselling which can be used to try to minimise risk factors which could prevent the onset of Sz

Question 10

what’re neural correlates

Answer 10

there are brain areas, structures or functions which appear related to Sz. in particular, dopamine (DA) has been found to be strongly associated with the illness

Question 11

what’re functions that dopamine plays a role in

Answer 11

pleasure/reward seeking behaviour
social functioning
movement
cognition

Question 12

what did Seeman find in the original dopamine hypothesis

Answer 12

• Sz patients’ neurotransmitters work differently
• dopamine is an excitatory neurotransmitter associated with pleasure
• unusually high levels are associated with Sz, positive symptoms in particular
• messages from neurons that transmit dopamine fire too easily/often in Sz patients
• Sz patients are thought to have abnormally high levels of D2 receptors on post-synaptic neurons, resulting in more dopamine binding and neurons firing

Question 13

what symptom is associated with high levels of dopamine

Answer 13

hyperdopaminergia, in the sub-cortical areas of the brain such as Broca’s area (can lead to auditory hallucinations)

Question 14

what symptom is associated with low levels of dopamine

Answer 14

Hypodopaminergia, in the cortical area of the brain, eg the PFC

Question 15

what is the updated dopamine hypothesis, by Davis

Answer 15

• high levels of dopamine aren’t found in all Sz patients, and the modern drug clozapine, wish very little DA-blocking activity, is effective against Sz.
• suggests that hypodopaminergia can also explain Sz but for negative symptoms
• therefore both too high/low levels of DA in different brain areas are associated with Sz symptoms
• It has also been suggested that Cortical hypodopaminergia can cause subcortical hyperdopaminergia

Question 16

what supports the role of dopamine in Sz

Answer 16

-the role of amphetamines: increase DA and worsened Sz symptoms and induced symptoms in non Sz patients
-antipsychotic drugs: reduce DA activity and the symptom intensity
-candidate genes: some act on DA production or receptors
-therefore strongly suggests DA’s involvement in Sz symptoms

Question 17

what supports the role of glutamate in Sz, weakening the neural correlates approach

Answer 17

-Post mortems and brain scans have shown consistently higher levels of the neurotransmitter glutamate in patients with Sz
-some candidate genes produce/raise glutamate levels
- this is a limitation because an equally strong cause to DA can be made for the role of other neurotransmitter’s, such as Glutamate

Question 18

what’re other, smaller evals for neural correlates

Answer 18

+ Lab study
- Biologically reductionist
- Deterministic

Question 19

what is a limitation of the genetic explanation for Sz

Answer 19

there are clearly environmental factors that too have a role:
- Birth complications cause heightened chance of Sz development
- Smoking cannabis in teenage years also heightens Sz risk
-67% of people with Sz and other related psychotic disorders reported at least 1 childhood trauma, contrasting to 38% of people in a control sample without Sz