The autism spectrum, also called autism spectrum disorders (ASD) or autism spectrum conditions (ASC), with the adjective autistic sometimes replacing the noun autism, is a spectrum of psychological conditions characterized by widespread abnormalities of social interactions and communication as well as restricted interests and repetitive behaviour.
The three forms of ASD are:
- Classic autism
- Asperger syndrome
- Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS), sometimes called atypical autism.
Autism forms the core of the autism spectrum disorders. Asperger syndrome is closest to autism in signs and likely causes; unlike autism, people with Asperger syndrome have no significant delay in language development. PDD-NOS is diagnosed when the criteria are not met for a more specific disorder. Some sources also include Rett syndrome and childhood disintegrative disorder, which share several signs with autism but may have unrelated causes; other sources combine ASD with these two conditions into the pervasive developmental disorders. According to the National Autistic Society of the United Kingdom, pathological demand avoidance syndrome belongs and is increasingly being recognised as belonging to the autistic spectrum.
The terminology of autism can be bewildering. Autism, Asperger syndrome, and PDD-NOS are sometimes called the autistic disorders instead of ASD, whereas autism itself is often called autistic disorder, childhood autism, or infantile autism. Although the older term pervasive developmental disorder and the newer term autism spectrum disorder largely or entirely overlap, the former was intended to describe a specific set of diagnostic labels, whereas the latter refers to a postulated spectrum disorder linking various conditions. ASD, in turn, is a subset of the broader autism phenotype (BAP), which describes individuals who may not have ASD but do have autistic-like traits, such as avoiding eye contact. Some autism are severe or moderate or light.
The defining characteristics of autism spectrum disorders are qualitative impairments of social communication and interaction, along with restricted and repetitive activities and interests. Individual symptoms occur in the general population and appear not to associate highly, without a sharp line separating pathological severity from common traits. Other aspects of ASD, such as atypical eating, are also common but are not essential for diagnosis; they can affect the individual or the family.
An estimated 0.5% to 10% of individuals with ASD show unusual abilities, ranging from splinter skills such as the memorization of trivia to the extraordinarily rare talents found in autistic savants.
Making and maintaining friendships often proves to be difficult for children with autism. For them, the quality of friendships, not the number of friends, predicts how lonely they are, despite the common belief that they prefer to be alone. Being on the autism spectrum does not keep children from understanding race and gender stereotypes in a society; like normal children they can learn aspects of stereotypical behaviour by observing their parents' actions.
The main goals of treatment are to lessen associated deficits and family distress, and to increase quality of life and functional independence. No single treatment is best and treatment is typically tailored to the child's needs. Intensive, sustained special education programmes and behaviour therapy early in life can help children acquire self-care, social, and job skills. Available approaches include applied behaviour analysis (ABA), developmental models, structured teaching, speech and language therapy, social skills therapy, and occupational therapy. ABA therapy has a strong research base but it maybe limited by diagnostic severity and IQ.
Many popular therapies including auditory integration therapy, GFCF diets, and chelation have repeatedly been shown to be ineffective and are not considered evidence-based practices.
Most recent reviews tend to estimate a prevalence of 1–2 per 1,000 for autism and close to 6 per 1,000 for ASD; because of inadequate data, these numbers may underestimate ASD's true prevalence. PDD-NOS's prevalence has been estimated at 3.7 per 1,000, Asperger syndrome at roughly 0.6 per 1,000, and childhood disintegrative disorder at 0.02 per 1,000. The number of reported cases of autism increased dramatically in the 1990s and early 2000s. This increase is largely attributable to changes in diagnostic practices, referral patterns, availability of services, age at diagnosis, and public awareness, though as-yet-unidentified environmental risk factors cannot be ruled out, and the available evidence does not rule out the possibility that autism's true prevalence has increased.
- World Health Organization. International Statistical Classification of Diseases and Related Health Problems. 10th ed. (ICD-10). 2006 [cited 2007-06-25]. F84. Pervasive developmental disorders.
- Lord C, Cook EH, Leventhal BL, Amaral DG. Autism spectrum disorders. Neuron. 2000;28(2):355–63. doi:10.1016/S0896-6273(00)00115-X. PMID 11144346.
- American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 4th ed., text revision (DSM-IV-TR). 2000. ISBN 0-89042-025-4. Diagnostic criteria for 299.80 Asperger's Disorder (AD).
- National Institute of Mental Health. Autism spectrum disorders (pervasive developmental disorders); 2009 [cited 2009-04-23].
- Freitag CM. The genetics of autistic disorders and its clinical relevance: a review of the literature. Mol Psychiatry. 2007;12(1):2–22. doi:10.1038/sj.mp.4001896. PMID 17033636.
- Piven J, Palmer P, Jacobi D, Childress D, Arndt S. Broader autism phenotype: evidence from a family history study of multiple-incidence autism families [PDF]. Am J Psychiatry. 1997;154(2):185–90. PMID 9016266.
- Klin A. Autism and Asperger syndrome: an overview. Rev Bras Psiquiatr. 2006;28(suppl 1):S3–S11. doi:10.1590/S1516-44462006000500002. PMID 16791390.
- Frith U, Happé F. Autism spectrum disorder. Curr Biol. 2005;15(19):R786–90. doi:10.1016/j.cub.2005.09.033. PMID 16213805.
- London E. The role of the neurobiologist in redefining the diagnosis of autism. Brain Pathol. 2007;17(4):408–11. doi:10.1111/j.1750-3639.2007.00103.x. PMID 17919126.
- Filipek PA, Accardo PJ, Baranek GT et al. The screening and diagnosis of autistic spectrum disorders. J Autism Dev Disord. 1999;29(6):439–84. doi:10.1023/A:1021943802493. PMID 10638459.
- Treffert DA. Wisconsin Medical Society. Savant syndrome: an extraordinary condition—a synopsis: past, present, future; 2006 [cited 2008-03-24].
- Burgess AF, Gutstein SE. Quality of life for people with autism: raising the standard for evaluating successful outcomes. Child Adolesc Ment Health. 2007;12(2):80–6. doi:10.1111/j.1475-3588.2006.00432.x.
- Hirschfeld L, Bartmess E, White S, Frith U. Can autistic children predict behavior by social stereotypes? Curr Biol. 2007;17(12):R451–2. doi:10.1016/j.cub.2007.04.051. PMID 17580071. Lay summary: ScienceDaily, 2007-06-19.
- Myers SM, Johnson CP, Council on Children with Disabilities. Management of children with autism spectrum disorders. Pediatrics. 2007;120(5):1162–82. doi:10.1542/peds.2007-2362. PMID 17967921. Lay summary: AAP, 2007-10-29.
- Shreck, K. A., Metz, B., Mulick, J.A. & Smith, A. (2000) Making it fit: A Provocative Look at Models of Early Intensive Behavioral Intervention for Children with Autism. The Behavior Analyst Today, 1(3), 27-32. 
- Mary Jane Weiss and Lara Delmolino (2006): The Relationship Between Early Learning Rates and Treatment Outcome For Children With Autism Receiving Intensive Home-Based Applied Behavior Analysis. The Behavior Analyst Today, 7(1), 96 - 105 
- Newschaffer CJ, Croen LA, Daniels J et al. The epidemiology of autism spectrum disorders [PDF]. Annu Rev Public Health. 2007 [cited 2009-10-10];28:235–58. doi:10.1146/annurev.publhealth.28.021406.144007. PMID 17367287.
- Caronna EB, Milunsky JM, Tager-Flusberg H. Autism spectrum disorders: clinical and research frontiers. Arch Dis Child. 2008;93(6):518–23. doi:10.1136/adc.2006.115337. PMID 18305076.
- Fombonne E. Epidemiology of pervasive developmental disorders. Pediatr Res. 2009;65(6):591–8. doi:10.1203/PDR.0b013e31819e7203. PMID 19218885.
- Wing L, Potter D. The epidemiology of autistic spectrum disorders: is the prevalence rising? Ment Retard Dev Disabil Res Rev. 2002;8(3):151–61. doi:10.1002/mrdd.10029. PMID 12216059.
- Rutter M. Incidence of autism spectrum disorders: changes over time and their meaning. Acta Paediatr. 2005;94(1):2–15. doi:10.1111/j.1651-2227.2005.tb01779.x. PMID 15858952.
- Baron IS. Autism Spectrum Disorder: complex, controversial, and confounding. Neuropsychol Rev. 2008;18(4):271–2. doi:10.1007/s11065-008-9070-1. PMID 18846426.
- For more information about Sensory Integration please visit www.sensoryintegration.org.uk
- For a short documentary about autism see BBC Four's 1992 Video here http://www.youtube.com/thefamilarity#p/u/2/PrViCkYF-lY