Childhood autism, also known as childhood autism, is a group of psychodevelopmental disorders that begin before the age of 3 years and are characterized by social interaction disorders, communication disorders, and restricted, stereotyped, repetitive behaviors, and is the most representative of pervasive developmental disorders. Pervasive developmental disorders include childhood autism, Asperge’s syndrome, Rett’s syndrome, childhood disintegrative disorder, atypical autism, and other unspecified pervasive developmental disorders. Currently, there is an international trend to collectively refer to childhood autism, Asperger’s syndrome and atypical autism as autism spectrum disorders, and the principles of diagnosis, treatment and rehabilitation are basically the same. Epidemiology Childhood autism is an increasingly common disorder of mental development. The results of the Second National Sample Survey of Persons with Disabilities show that mentally disabled (including multiple) children aged 0-6 years in China account for 1.10 per thousand of the total number of children aged 0-6 years, or about 111,000 people, of whom 36.9%, or about 41,000 people, are mentally disabled as a result of autism. Childhood autism is more common in boys, and its prevalence is independent of race, geography, culture and level of socioeconomic development. Etiology Childhood autism is a biologically based mental developmental disorder caused by a variety of factors and occurs in genetically predisposed individuals in response to specific environmental factors. Genetic factors are the main cause of childhood autism. Environmental factors, especially exposure during the critical period of fetal brain development, also increase the likelihood of developing the disorder.