What is the rate of concordance for schizophrenia in identical twins?

Concordance rates between monozygotic twins vary in different studies, approximately 50%; whereas dizygotic twins was 17%. Some twin studies (Koskenvuo et al; Hoeffer et al) have found rates as low as 11.0%-13.8% among monozygotic twins, and 1.8%-4.1% among dizygotic twins.