Genetic explanation

• Concordance rate

  The rate of probability that two people with shared genes will develop the same organic disease.
• Gottesman

  Looked at the heritability of SZ.

  Concordance rates:

  Parents 6%

  Siblings 9%

  DZ twins 17%

  MZ twins 48%
• Gottesman & Shields

  Found a concordance rate of 42% for MZ and 9% for DZ.
• Heston 


  Compared 47 children of SZ mothers who were adopted before the age of one month with a control group of 47 children raised by non SZ mothers.

  10% of the children with SZ mothers developed SZ compared to none of the controls.
• Tienari et al

  Compared 112 cases of adopted children who had biological mothers who had been diagnosed with SZ with 135 adopted children who had non SZ biological mothers.

  7% of these children (112) developed SZ compared to 1.5% of controls.
• Strengths of the genetic explanation

  Supporting evidence

  Deterministic
• Weaknesses of genetic explanation

  Difficult to separate nature and nurture when researching families.

  Concordance rates are not 100% meaning their are other influencers.

  Diathesis stress model may offer a better explanation (without environmental stressors, genetics are unlikely to lead to SZ).