Biological explanations for Schizophrenia (Genetics)

Question 1

Family studies A01 - Gottesman Study

Answer 1

-family studies have established Dz more common in biological relatives
-the closer degree of relatedness, the greater the risk
-sz tends to run in families
- Gottesman:
-Children with 1 Sz parent had 13% chance
- siblings (a sibling had Sz) 9% risk
- increased to 48 % if identical twin had Sz
- 17% non-identical twin

Question 2

Twin studies A01- Gottesman and Shields study

Answer 2

• twin studies often suggest genetic cause of Sz
• identical twins have higher concordance rates for Sz than non-identical: genes play a factor
  -Gottesman and Shields:
  
  • compared Mz and Dz twins (1 had sZ)
  • concordance rates Mz (identical): 42%
    -concordance rates Dz (non-identical): 9%

Question 3

Adoption studies A01- Tienari et al study

Answer 3

• adoption studies found link btwn genes and Sz
  -Tienari et al
  
  • Finland
  • 164 adoptees whose biological mother diagnosed with Sz, 6.7% also have Sz
    
    • 2 % of 197 control adoptees (mothers didn’t have Sz)
    • suggests not sharing same environment as biological mothers, adoptees still at risk of developing Sz if mothers also had it: GENETIC

Question 4

A03- strengths for genetic explanation

Answer 4

• Heston provides support
  - 10.6% adults who had Sz mothers developed S whereas none of control group did
• Sz affects 1 % population- strong support as implies genetics
• identifying Candidate genes may be involved in onset of Sz can lead to applications
• eg. Gene mapping- establishing locations of genes on chromosomes, following inheritance patterns
• can accurately and consistently diagnose Sz

Question 5

A03- weakness for genetic explanation

Answer 5

-If sz has entirely genetic basis then would expect concordance rates to be 100%
- but Gottesman and Shields found 42% in Mz and 9% in Dz - suggests should be other factors

• most likely genes create vulnerability for Sz rather than causing it
  
  • May possess Sz genes (a diathesis), but condition is only triggered by biological or environmental effects (eg. Stress)