Gottesman (1991)- found concordance rates of 17% for DZ twins and 48% for MZ twins.
Twin studies
Concordanceratesarenever100%.
Sample size
MZ twins are rare and only 1% of them would be expected to have schizophrenia.
Twin studies
Twins also share an environment so it is difficult to determine what is due to genetics.
Supporting evidence + limitation
Tienari (1991)- found that 10% of children developed SZ if their biological mother had it compared to 1% of children who developed it when they had no family history of SZ.
