3.3.2.1 Genetic Basis of Schizophrenia

• Family studies confirm that the risk of schizophrenia increases as genetic similarity increases
• Genetic Similarity: Gottesman (1991)

  • Large-scale study
  • Aunt = 2%
  • Sibling = 9%
  • Identical twin = 48%
• Candidate Genes = genes that are associated with a particular disorder.
• • Schizophrenia is polygenic
  • Multiple genes involved in development of schizophrenia
  • Schizophrenia is aetiologically heterogenous
  • Ripke et al (2014) = 108 seperate variations
• Aetiologically Heterogenous = different causes of the same disorder
• Mutation in parental DNA by radiation/poison/viral infection
• Mutation: Brown et al (2000)

  • Increased paternal age links to increased risk of sperm mutation
  • Risk of 0.7% = Fathers under 25
  • Risk of 2% = Fathers over 50
• Strength = Research support

  • Hiker et al (2018)
  • Concordance rate of 33% = MZ twins
  • Concordance rate of 7% = DZ twins
  • Genetic vulnerability & similarity
• Weakness = Environmental Factors

  • Morkved et al (2017) = 67% risk with trauma & schizophrenia;
  • Concordance rate of 7% = DZ twins
  • Genetic vulnerability & similarity