Les schizophrénies, maladies du neurodéveloppement

Developmental anomalies have been identified as risk factors for a future schizophrenic illness: low weight at birth, congenital malformations, delayed motor and social learning. Cognitive deficits and neurological soft signs belong to the indices of the schizophrenic spectrum. Neuroimaging has visualized various structural abnormalities present from the very beginning of schizophrenia. These structural changes may represent an exacerbation of normal neurodevelopmental processes. Moreover, vulnerability genes for schizophrenia are involved at different stages of neurodevelopment: the best studied associations are dysfunctional variants of DISC-1 and neuroregulin-1 genes, the role of other genes (dysbindin, BDNF, reelin…) remaining more widely debated. Lastly, the observation of structural chromosomal anomalies in 15% of patients suffering from schizophrenia (versus 5% of controls), more frequent in early onset schizophrenia (32% of cases) suggests a neurodevelopmental cause. Such a dynamic understanding of schizophrenia is consistent with what we know about cerebral plasticity along the life span. This does not preclude the search for cues of degenerative mechanisms. The issue now is a better characterization of the vulnerable phenotype for screening procedures to be implemented prior to disease onset.