What is the concordance rate for schizophrenia in monozygotic and dizygotic twins? What is general level of concordance for twins and is it higher for monozygotic twins?
What research is available on this?
The Wikipedia article seems to provide a summary of this information with links to the primary literature

http://en.wikipedia.org/wiki/Causes_of_schizophrenia#Genetics


  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, however.


References


Koskenvuo M, Langinvainio H, Kaprio J, Lönnqvist J, Tienari P; Langinvainio; Kaprio; Lönnqvist; Tienari (1984). "Psychiatric hospitalization in twins". Acta Genet Med Gemellol (Roma) 33 (2): 321–32. PMID 6540965.
Hoeffer A, Pollin W; Pollin (November 1970). "Schizophrenia in the NAS-NRC panel of 15,909 veteran twin pairs". Arch Gen Psychiatry 23 (5): 469–77. doi:10.1001/archpsyc.1970.01750050085012. PMID 5478575.