Autism is a developmental disorder that is more commonly diagnosed in children under 3 years old. Autism is characterized by reduced social interaction and communication, as well as limited, repetitive, and stereotyped behavior. The symptoms of the disease often range from social and linguistic communication problems, including chronic isolation and lack of verbal response, to unusual responses to sensory stimuli or mood and behavioral disorders that can lead to aggression, irritability, and self-injury. Autism is not a psychiatric disorder, it falls in the category of pervasive developmental disorders.
Autism seems to have a strong genetic basis, although the genetics of autism are complex and it is unclear whether it is due to rare mutations or rare combinations of common genetic variants. It also seems that a wide range of environmental factors (pesticides, heavy metals, intestinal microbiome, etc.), which affect both the mother during pregnancy and the child itself, can contribute to the onset of autism. Because there are many types of autism that vary widely in their characteristics, each specific case often has a unique set of biochemical factors that contribute to the onset and severity of symptoms.