Biological explanations of SZ

Question 1

genetics

Answer 1

genes consist of DNA strands which produce instructions for general physical features of an organism

Question 2

neural correlates

Answer 2

patterns of structure or activity in the brain that occur in conjunction with an experience and may be implicated in the origins of that experience

Question 3

dopamine

Answer 3

a neurotransmitter that generally has an excitatory effect and is linked to the sensation of pleasure

Question 4

Gottesman - family studies

Answer 4

if someone’s aunt is a schizophrenic then the likelihood is 2%, 9% for a sibling and 48% for an identical twin.

Question 5

family studies representing both nature and nurture

Answer 5

family members also share aspects of their environment

Question 6

cadidate genes

Answer 6

• Must then be identified
• Early research looked for single genetic variation
• But a number of genes are actually involved (polygenic)
• Most likely genes would be those coded for neurotransmitters eg dopamine

Question 7

Ripke et al’s large study combined all genetics related data to wider studies

Answer 7

• Genetic makeup of 37000 people were compared to 113000 controls
• 108 separate variations were associated with slight increased risk of schizophrenia

Question 8

aetiologically heterogeneous

Answer 8

meaning combination of factors

Question 9

what is mutation casued by

Answer 9

Mutation of parental DNA can be caused by radiation, poison or viral infection, which can lead to schizophrenia

Question 10

where does evidence for mutation come from

Answer 10

correlations of paternal age and risk of schizophrenia, increasing from around 0.7% with fathers under 25 to 2% in fathers over 50 → Brown et al

Question 11

research support for the genetic basis of sz

strength

Answer 11

• Adoption studies like Tienari et al show that biological children of parents with schizophrenia are at heightened risk even if they grow up in an adopted family
• Twin study by Hilker et al showed concordance rate of 33% for identical twins and 7% for non-identical
  Some people are more at risk of schizophrenia according to their genetics.

Question 12

environmental factors affecting the genetic basis of sz

limitation

Answer 12

• Biological and psychological influences
• Biological risk factors include birth complications (Morgan) and smoking cannabis in teen years (Di Forti)
• Psychological risk factors include childhood trauma
• Study showed 67% of schizophrenics had one childhood trauma compared to 38% in matched group of non-psychotics
  Genes alone cannot provide a complete explanation

Question 13

Neural correlates of schizophrenia

Answer 13

Dopamine is the best known neural correlate for schizophrenia as it is important in the functioning of several brain systems related to the symptoms of schizophrenia.

Question 14

what was the origional dopamine hypothesis based on?

Answer 14

the discovery that drugs used to treat schizophrenia (antipsychotics which reduce DA) caused symptoms similar to those with Parkinsons, a condition associated with low DA levels (Seeman).

Question 15

what does the origional dopamine hypothesis suggest

Answer 15

schizophrenia is caused by high levels of DA in subcortical areas of the brain. For example, an excess of DA receptors in Broca’s area might cause speech poverty or auditory hallucinations.

Question 16

Davis et al proposed the addition of cortical hypodopaminergia, which means low DA in the brain’s cortex. Can explain some symptoms:

Answer 16

• Low DA in prefrontal cortex can explain thinking problems
• Cortical hypodopaminergia leads to subcortical hyperdopaminergia

Question 17

what do current verions of the dopamine hypothesis do

Answer 17

tries to explain the origins of abnormal DA function. Both genetic variations and early experiences of stress, both psychological and physical, can make some people more sensitive (Howes et al)

Question 18

evidence for dopamine in the neural explanations of sz

strength

Answer 18

• Amphetamines increase DA and worsen schizophrenia symptoms in people without (Curran et al)
• Antipsychotic drugs reduce DA activity and intensity of symptoms (Tauscher et al)
• Some candidates genes act on the production of DA or DA receptors
  Suggesting dopamine is involved

Question 19

glutamate - central role

limitation

Answer 19

• Post-mortem and live scanning consistently find raised levels of the neurotransmitter glutamate in several brain regions of schizophrenics (McCutcheon)
• Several candidate genes are believed to be involved in glutamate production or processing
  Equally strong case can be made for other neurotransmitters