summary 
The determinants and disease mechanisms of schizophrenia are largely unknown. This article discusses two genetic and two epigenetic models and examines to what extent they are capable of predicting epidemiological patterns, providing insight into the determinants and disease mechanisms, and to what extent they are based on empirical findings. The proposed litmus test is whether they are able to provide an explanation for discordance in monozygotic twins. The main lines of a synthetic model are presented on the basis of the assessments.