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.
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).
Early speech or behavioral interventions can help children with autism gain self-care, social and communication skills. Although there is no known cure, there have been cases of children who have recovered from the condition. Not many children with autism live independently after reaching adulthood, though some are successful. An autistic culture has developed, with some individuals seeking a cure and others believing autism should be accepted as a difference and not treated as a disorder.
Globally, autism is estimated to affect 24.8 million people as of 2015. In the 2000s, the number of people affected was estimated at 1–2 per 1,000 people worldwide. In the developed countries, about 1.5% of children are diagnosed with ASD as of 2017, a more than doubling from 1 in 150 in 2000 in the United States. It occurs four to five times more often in boys than girls. The number of people diagnosed has increased dramatically since the 1960s, partly due to changes in diagnostic practice; the question of whether actual rates have increased is unresolved.