<Tr> <Th> Prognosis </Th> <Td> Frequently poor </Td> </Tr> <Tr> <Th> Frequency </Th> <Td> 24.8 million (2015) </Td> </Tr> <P> Autism is a developmental disorder characterized by troubles with social interaction and communication and by restricted and repetitive behavior . Parents usually notice signs in the first two or three years of their child's life . These signs often develop gradually, though some children with autism reach their developmental milestones at a normal pace and then worsen . </P> <P> Autism is caused by a combination of genetic and environmental factors . Risk factors include certain infections during pregnancy, such as rubella, as well as valproic acid, alcohol or cocaine use during pregnancy . Controversies surround other proposed environmental causes, for example the vaccine hypotheses, which have been disproven . Autism affects information processing in the brain by altering how nerve cells and their synapses connect and organize; how this occurs is not well understood . In the DSM - 5, autism is included within the autism spectrum (ASDs), along with Asperger syndrome, which is less severe, and pervasive developmental disorder not otherwise specified (PDD - NOS). </P>

What is the meaning of the word autism