Genetic Explanations

• SZ is heritable through transmission of DNA/genes
• One candidate gene that has been proposed to be linked with SZ is PCM1 (associated with orbitofrontal volume deficit which links to thought disorders)
• What number of genetic variations did Ripke propose there could be which are associated with an increased risk of SZ?

  Ripke combined data from many studies and found 108 genetic variations which were associated with an increased risk of SZ
• Schizophrenia could be polygenic
• The increased risk could be the interaction between NRG3 (associated with attention deficits) and NRG1 (associated with psychomotor agitation which is a state of restlessness and anxiety which results in restlessness and unintentional movements)
• What did Gottesman's study find?

  1% probability of developing SZ in general population

  2% if an aunt/uncle has it

  9% if a sibling has it

  17% if a dyzgotic twin (DZ) has it

  48% if a monozygotic twin (MZ) has it
• How does Brown's findings show how genetic mutation can be a reason for developing SZ when having no family history of it?

  Genetic mutation could explain why some with no family history develop SZ. For example, the risk of sperm mutation increases with age. Brown found a 0.7% risk of sperm mutation if a father was under 25, and a 2% risk if the father was over 50.
• Genetic effects may be overstated, perhaps it is nature and nurture. Use MZ twins to explain this

  MZ twins may have such high concordance because they have a shared microenvironment with their twin and also, people may learn from family members as they are likely to be sharing the same environment.
• What did Tienari find about the relationship between risk of SZ and biological children in adoptive homes?


  Tienari found biological children of people with SZ are more at risk, even if they grow up in an adoptive family, suggesting genes are important
• If genetics are to blame, families will be less stigmatised as they are more obviously not to blame
• Mørkved et al. found that 67% of people with SZ and related psychotic disorders reported at least one childhood trauma, compared with 38% of people with non-psychotic mental health issues suggesting that genetic factors on their own can't explain SZ fully