Background: A previous study demonstrated a 40% higher rate of schizophrenia in dizygotic twins than in the general population. The aim of the present study is to evaluate whether genes influencing the rate of dizygotic twinning and genes of importance for developing schizophrenia can be associated.
Method: Through record linkage between The Danish Twin Register, The Danish Psychiatric Central Register, and The Danish Civil Registration System, the rate of schizophrenia in singleton siblings of dizygotic and monozygotic twins was compared with the rate in siblings of singletons.
Results: The rate of first admission to hospital for schizophrenia in siblings of dizygotic twins was 35% greater than the rate in siblings of singletons. The result was statistically significant (p = 0.04). The rate in siblings of monozygotic twins was not increased.
Conclusion: The results are in accordance with a theory of a linkage between genes influencing the rate of dizygotic twinning and genes influencing the threshold for developing schizophrenia.
Copyright 2002 Elsevier Science B.V.