Genes

• Rosenthal (1963)?

  Studied quadruplets- all 4 girls identical. All developed scz, although they differed in terms of age of onset and their precise symptoms. Known as Genain quadruplets. Probability of all 4 sisters developing scz by chance is 0.000001%. Had unpleasant upbringing, and parents showed clear signs of instability. Girls childhoods were disrupted due to inability of parents to care for them.
• What are the 3 main types of heritability studies?

  Family, twin and adoption studies.
• Claridge and Davis (2003)?


  Argued contribution of genetic influences is 1 of few factual certainties about scz. Even in absence of discovery of specific genes, this is clear from kinship data.
• Gottesman (1991)- Twin studies results?

  Found concordance rates between MZ twins was 48%, but only 17% for DZ twins. ( If 1 of the MZ twins has scz, there's 48% chance other twin will also have it). MZ and DZ twins both share environment, so higher concordance rate in MZ twins may be due to shared genes.
• Claridge and Davis (2003) twin studies?

  Reviewed twin studies into scz and reported concordance rates for MZ twins ranging from 0%-90%. Generally, concordance for MZ twins seems to be around 50%. ( Findings tend to be highly variable and fluctuating).
• Gottesman and Shields (1982)?


  Found heritability of scz varied depending upon severity of symptoms, with more severe cases of scz having higher concordance rates.
• What are the advantages of family studies?

  More generalisable to public. Members have different upbringings. Can see if scz has been passed down through family members.
• Gottesman and Bertelsen (1989)?


  Found people whose parent had identical twin with scz, had 17% chance of having scz themselves, whether or not parent had scz.
• What is the advantage of using adoption studies?

  Separates between nature & nurture. If children have high concordance rate with birth families, it would suggest genetic basis. If they have high concordance rate with adopted families, suggests environmental cause of scz.
• Tienari et al (2000)?


  Studied 164 adoptees whose biological mothers had been diagnosed with scz and found that 11 ( 6.7%) also received scz diagnosis, compared with just 4 (2%) of 197 in control adoptees born to non-scz mothers. Children at high genetic risk of scz tend to do well if adopted family provide supportive environment- better than those who don't have genetic risk but brought up in unsupportive environment.
• O'Donovan et al (2014)?

  Identified 108 specific locations on human genome linked with scz, 83 of which had never been reported before. Sample of over 80,000 Scz people and controls. Genes identified were involved with brain tissue and were active in immune system.
• What is the diathesis stress model?

  Suggests cause of illness is both genetic & environmental. May inherit genetic predisposition to illness (diathesis) but won't develop illness unless there's environmental trigger (stress). E.g, upbringing, urbanicity, family dynamics, etc.