Autism also called autistic disorder is a neurodevelopmental disorder that manifests itself before the age of three years Children with autism are marked by impairments in social interaction, impairments in communication, and restricted and repetitive behaviour These three characteristics reflect Leo Kanner's first reports of autism emphasizing autistic aloneness and insistence on sameness Autism is one of the five pervasive developmental disorders PDD or autism spectrum disorders ASD which have no outward physical characteristics Diagnosis is typically based on a complete patient history and physical and neurological evaluation Estimates of prevalence vary widely Most recent reviews estimate a prevalence of 12 per 1,000 for autism and close to 6 per 1,000 for ASD The number of diagnosed autism cases has increased dramatically since the 1980s. Some of this increase is undoubtedly due to better diagnosis wider public awareness of the condition and changes in diagnostic criteria It is debatable whether prevalence has increased as well as it is hard to quantify estimates of diagnostic effects and nearly impossible to measure changes in risk profiles given how little is known about the disorder's underlying causes Some individuals with autism are opposed to attempts to find a cure for autism These people see autism as part of who they are and in some cases they perceive treatments and attempts of a cure to be unethical Asperger syndrome