[Genetic hypothesis of schizophrenia]

It is now well demonstrated from family, adoption or twin studies, that genetic factors are involved in schizophrenia. Yet, the nature of these factors remains unknown. The disappointing results of the classical linkage studies are explained by the complex non mendelian inheritance, involving several genes interacting with environmental and/or maturation processes, and the heterogeneity of the clinical expression. The identification of genes having an influence on schizophrenia requires thus new strategies including statistical analysis with no assumption on the inheritance mode (non parametric methods) and the dissection of the heterogeneous syndrome using endophenotypes and/or relevant clinical features. Beside the hypothesis of a dysfunctional neurotransmission in schizophrenia (i.e. dopaminergic), evidence suggests that genes involved in neurodevelopment could also be candidate. The observation of caryotypic anomalies could also lead to new candidate regions or genes.