After it was recognised as a distinct disorder, reports of autism cases substantially increased, which was largely attributable to changes in diagnostic practices, referral patterns, availability of services, age at diagnosis, and public awareness (particularly among women).Several other conditions were commonly seen in children with autism. They include:

Intellectual disability. The percentage of autistic individuals who also met criteria for intellectual disability has been reported as anywhere from 25% to 70%, a wide variation illustrating the difficulty of assessing intelligence of individuals on the autism spectrum. In comparison, for PDD-NOS the association with intellectual disability was much weaker, and by definition, the diagnosis of Aspergers excluded intellectual disability. Minor physical anomalies are significantly increased in the autistic population. Preempted diagnoses. Although the DSM-IV ruled out the concurrent diagnosis of many other conditions along with autism, the full criteria for Attention deficit hyperactivity disorder (ADHD), Tourette syndrome, and other of these conditions were often present. As a result, modern ASD allows for these diagnoses. History
The New Latin word autismus (English translation autism) was coined by the Swiss psychiatrist Eugen Bleuler in 1910 as he was defining symptoms of schizophrenia. He derived it from the Greek word autós (αὐτός, meaning "self"), and used it to mean morbid self-admiration, referring to "autistic withdrawal of the patient to his fantasies, against which any influence from outside becomes an intolerable disturbance". The word autism first took its modern sense in 1938 when Hans Asperger of the Vienna University Hospital adopted Bleulers terminology autistic psychopaths in a lecture in German about child psychology.
Individual symptoms of autism occur in the general population and appear not to associate highly, without a sharp line separating pathologically severe from common traits. Social development
Autistic people have social impairments and often lack the intuition about others that many people take for granted. Unusual social development becomes apparent early in childhood. Autistic infants show less attention to social stimuli, smile and look at others less often, and respond less to their own name. Autistic toddlers differ more strikingly from social norms; for example, they have less eye contact and turn-taking, and do not have the ability to use simple movements to express themselves, such as pointing at things. Three- to five-year-old autistic children are less likely to exhibit social understanding, approach others spontaneously, imitate and respond to emotions, communicate nonverbally, and take turns with others. However, they do form attachments to their primary caregivers. Most autistic children displayed moderately less attachment security than neurotypical children, although this difference disappears in children with higher mental development or less pronounced autistic traits. Children with high-functioning autism have more intense and frequent loneliness compared to non-autistic peers, despite the common belief that autistic children prefer to be alone. Making and maintaining friendships often proves to be difficult for autistic people. For them, the quality of friendships, not the number of friends, predicts how lonely they feel. Functional friendships, such as those resulting in invitations to parties, may affect the quality of life more deeply.