Childhood-onset schizophrenia (COS) is a rare but severe psychiatric disorder with important individual, family and societal consequences. Its prevalence is approximately 2 per 10.000 in the general population and the incidence of COS increases with age.

The main objective of our study was to evaluate the prevalence of COS in French medical-social institutions or psychiatric day hospitals for children and adolescents in the PACA region. The secondary objectives were:

1. (1) to estimate the prevalence of children with both COS and autism diagnosis,

2. (2) to characterize clinical and neurocognitive presentation of COS using the evaluation of intensity of positive and negative symptoms (PANSS, SANS), of thought disorganization (TLC), of cognitive functioning, and of attention and executive functions (verbal fluency, TMT A, TMT B).

Subjects were patients from medical-social and psychiatric care centers for children and adolescents in three PACA sub-regions in the south-east of France. The study included French speaking girls and boys between 7 and 18 years old, registered in a partner structure of the study, and presenting an IQ > 35 (WISC-IV). The study design was constituted by two phases: the first one was the categorical diagnostic phase using the psychosis section of the Kiddie-SADS Present and Lifetime Version. The second phase consisted of the dimensional COS diagnosis and neurocognitive exploration for the subjects fulfilling the DSM-IV diagnostic criteria for schizophrenia.

The diagnosis of COS was not exceptional in this population. Most subjects diagnosed with COS also presented autism diagnosis and mental retardation.