Explanations of Scizophrenia

• Genetics suggests that Sz is genetic. If a person has more similar genes to someone with Sz, they are more likely to have Sz, expected most in mz twins. It has been researched by family, twin and adoption studies. There is no one clear gene - it is likely to be a combination. Having the genes does not mean you will develop Sz
• What is the interactionist model?

  Diathesis stress - genetics create a vulnerability

  you need the correct genetics but also requires a trigger to develop the disorder (usually in the environment)

  genetics + trigger = switches on genes
• Family studies have established that Sz is more common among biological relatives.
• Who carried out family studies?

  Gottesman and Shield
• What did Gottesman and Shield's family studies find?

  children with 2 Sz parents had a concordance rate of 46%

  children with 1 Sz parent - 13%

  Siblings - 9%

  However it could be argues that the children were imitating learnt behaviour - SLT
• Who carried out twin studies?

  Gottesman and Shield and Joseph
• What did Gottesman and Shield's twin studies find?

  a concordance rate of MZ twins - 48%

  a concordance rate of DZ twins - 17%
• What did Joseph's twin studies find?

  Concordance rate for MZ twins - 40.4%

  Concordance rate for DZ twins - 7.4%
• What are the problems with twin studies?

  1. twins have the same environment - treated the same
  2. twins are uncommon - small sample size
  3. the overall childhood experience is different - share a room, cot - not generalisable to non-twins
  4. MZ not 100% and DZ not 50% (or half of whatever MZ is)
• Who conducted adoption studies?

  Tierani et al - adoption study in Finland
• Describe Tierani's study?

  164 Finish adoptees whose biological mother had been diagnosed with Sz
• How many of the adoptees also had a diagnosis of Sz?

  11 - 6.7%
• How many of the control 197 adoptees had Sz?

  4 - 2% - concluded that there is a genetic component
• Why are adoption studies useful?

  There is a difficulty disentangling genetic and environmental influences. Adoption studies allow us to study genetically related individuals reared apart
• What are some issues of adoption studies?

  1. the adoption process can be traumatic - some say Sz is caused by trauma
  2. there are extraneous variables depending on adoptive families - not everyone is adopted at the same age.
• Concordance rates in relatives from both family and twin studies can be explained by factors other than genetics:

  1. shared experiences - families tend to live together - especially twins
  2. are concordance rates due to genetics or due to shared experiences
  3. cannot untangle nature and nurture when we study families