Evaluation of Genetics and SZ

Question 1

+/- 61 patient sample

Answer 1

In a sample of 61 patients who were either MZ or DZ twins, on average, if one MZ twin had schizophrenia, then 42% of the time the other did too. In DZ twins, the average concordance rate was 17% - supports genetic predisposition. However, suggests not entirely genetically caused, as we would expect 100% concordance from MZ twins, suggesting the theory to be reductionist

Question 2

+ Adopted children with SZ and non-SZ biological mothers

Answer 2

Research has found that adopted children with biological mothers with SZ are more likely to develop SZ than adopted children with biological mothers without SZ - validates idea that SZ is more influence by genes than by environment

Question 3

+ Sullivan et al. meta-analysis

Answer 3

A meta-analysis by Sullivan et al. of twin studies found an 81% heritability for SZ - meta-analysis provides highly reliable and valid evidence for genetic cause of SZ

Question 4

• Tiwari et al. (family history)

Answer 4

Tiwary et al. pointed out that fewer than one third of SZ sufferers have a family history of SZ - refutes idea that SZ is entirely genetically caused

Question 5

• Nature-nurture interaction

Answer 5

SZ may be more to do with an interaction between nature and nurture (genes and environment - reductionist explanation that ignores role of environment

Question 6

• Controlling for environment

Answer 6

Twin and family studies fail to control for environmental influences - negates environmental influences which may contribute to SZ on top of genes