Biological explanations of schizophrenia

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  • Created by: KCharlish
  • Created on: 28-03-16 13:26

AO1 1 - Family studies

  • Gottesman - SZ is more common among biological relatives of a person with SZ than in the general population.
    • Greater the degree of genetic relatedness the greater the risk
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AO1 2 - Twin studies

If MZ twins are more similar in terms of SZ than DZ twins this suggests a strong genetic influcence.

  • Joseph - concordance rate of just 40% for MZ  twins and just over 7% for DZ twins.

More recent studies have found lower concordance rates for MZ twins. 

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AO1 3 - Dopamine hypothesis

Schizophrenics have abnormally high numbers of D2 dopamine receptors , resulting in dopamine neurons firing. 

May elad to problems of perception and thought found in SZ.

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AO1 4 - Enlarged ventricles

  • PET and MRI scans - many schizophrenics have enlarged ventricles.
  • Torrey - 15% bigger than normal
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AO2 1 - Evolutionary

  • Maladaptive traits would have been selcted out during the process of naturan selection - SZ would not exist. today.
  • Stevens and Price - the presence of a charismatic leaders with SZ could have influenced members to follow and form a new group.
  • 'group splitting hypothesis' argues that SZ is an extreme expression of an adaptive trait. 
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AO2 2 - Twin studies

  • Greater concordance rates may be due to the way in which MZ twins are treated more similarly - 'identity confusion'
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AO2 3 - Adoption studies

  • Tienari - adoptees whose biological mothers had SZ, 6.7% of these individuals also developed the disorder. Compared to 2% of adoptees born to non schizophrenics
    • supports the genetic explanation
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AO2 4 - Methodological problems

  • Support is found by broadening the definition to include non psychotic 'schizophrenia spectrum disorder'. Rather than restricting it to full blown SZ. 
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AO2 5 - Dopamine support

  • Amphetamines - dopamine antagonists which stimulate nerve cells and cause the synapse to be flooded with dopamine. 
    • Large doses have caused hallucinations and delusions. 
  • L-dopa is used to treat Parkinson's and raise dopamine levels
    • individuals have developed schizophrenic symptoms
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AO2 6 - Consequence not a cause

  • high levels of dopamine may be a consequence rather than a cause of SZ.
  • Haracz - post mortem studies; those who showed elevated dopamine levels received AP drugs shortly before death.
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AO2 7 - Enlarged ventricles

  • Enlarged ventricles may be an effect rather than the cause.
  • Lyon - as the dose of AP drugs increased it led to enlarged ventricles. 
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