Autism is a physical disorder linked to abnormal biology and chemistry in the brain. The exact causes of these abnormalities remain unknown, but this is a very active area of research. Genetic factors seem to be important. For example, identical twins are much more likely than fraternal twins or siblings to both have autism. Similarly, language abnormalities are more common in relatives of autistic children. Chromosomal abnormalities and other neurological problems are also more common in families with autism.
Researchers supported by NIMH and other National Institute of Health (NIH) institutes are studying how an autistic brain differs from a normal brain. Some researchers are investigating potential defects that occur during initial brain development; others are looking for defects in the brains of people already diagnosed with autism.
Recent neuroimaging studies have shown that a contributing cause for autism may be abnormal brain development beginning in the infant's first months. This "growth dysregulation" theory holds that the anatomical abnormalities seen in autism are caused by genetic defects in brain-growth factors. It is possible that sudden, rapid head growth in an infant may be an early warning signal that will lead to early diagnosis and effective biological intervention or possible prevention of autism.
Postmortem and magnetic resonance imaging (MRI) studies have shown that many major brain structures are implicated in autism. This includes the cerebellum, cerebral cortex, limbic system, corpus callosum, basal ganglia, and brain stem. Other research is focusing on the role of neurotransmitters such as serotonin, dopamine, and epinephrine.
Autism. Last reviewed 02/22/2007 Sources:
- National Institute of Mental Health Akshoomoff N, Pierce K, Courchesne E. (2002) The neurobiological basis of autism from a developmental perspective. Development and Psychopathology, 14: 613-634.
- Berument SK, Rutter M, Lord C, Pickles A, Bailey A. (1999). Autism Screening Questionnaire: diagnostic validity. British Journal of Psychiatry, 175: 444-451.
- Baird G, Charman T, Baron-Cohen S, Cox A, Swettenham J, Wheelwright S, Drew A. (2000). A screening instrument for autism at 18 months of age: A 6-year follow-up study. Journal of the American Academy of Child and Adolescent Psychiatry, 39: 694-702.
- Courchesne E. Carper R, Akshoomoff N. (2003). Evidence of brain overgrowth in the first year of life in autism. JAMA, 290(3): 337-344.
- Department of Health and Human Services. Mental Health: A Report of the Surgeon General. Rockville, MD: Department of Health and Human Services, Substance Abuse and Mental Health Services Administration, Center for Mental Health Services, National Institute of Mental Health, 1999.
- Ehlers S, Gillberg C, Wing L. (1999). A screening questionnaire for Asperger's syndrome and other high-functioning autism spectrum disorders in school-age children. Journal of Autism and Developmental Disorders, 29(2): 129-141.
- Filipek PA, Accardo PJ, Ashwal S, Baranek GT, Cook Jr. EH, Dawson G, Gordon B, Gravel JS, Johnson CP, Kallen RJ, Levy SE, Minshew NJ, Ozonoff S, Prizant BM, Rapin I, Rogers SJ, Stone WL, Teplin SW, Tuchman RF, Volkmar FR. (2000) Practice parameter: screening and diagnosis of autism. Neurology, 55: 468-479.
- Garnett MS, Attwood AJ. (1997). The Australian scale for Asperger's syndrome. In: Attwood, Tony. Asperger's Syndrome: A Guide for Parents and Professionals. London: Jessica Kingsley Publishers.
- Korvatska E, Van de Water J, Anders TF, Gershwin ME. (2002). Genetic and immunologic considerations in autism. Neurobiology of Disease, 9: 107-125.
- Lord C, Risi S, Lambrecht L, Cook EH, Leventhal BL, DiLavore PC, Pickles A, Rutter M. (2000). The autism diagnostic observation schedule-generic: a standard measure of social and communication deficits associated with the spectrum of autism. Journal of Autism and Developmental Disorders, 30(3): 205-230.
- Lovaas OI. Behavioral treatment and normal educational and intellectual functioning in young autistic children. Journal of Consulting and Clinical Psychology, 1987; 55: 3-9.
- McDougle CJ, Stigler KA, Posey DJ. (2003). Treatment of aggression in children and adolescents with autism and conduct disorder. Journal of Clinical Psychiatry, 64 (supplement 4): 16-25.
- McEachin JJ, Smith T, Lovaas OI. Long-term outcome for children with autism who received early intensive behavioral treatment. American Journal on Mental Retardation, 1993; 97: 359-372.
- National Institutes of Health, National Library of Medicine, MedlinePlus, 2007. Autism. www.nlm.nih.gov/medlineplus/ency/article/001526.htm
- Newschaffer CJ (2003). (Johns Hopkins Bloomberg School of Public Health). Autism Among Us: Rising Concerns and the Public Health Response [Video on the Internet]. Public Health Training Network, 2003 June 20. Available from: www.publichealthgrandrounds.unc.edu/autism/webcast.htm.
- Powers, M. D. (2000). What Is Autism? In: Powers MD, ed. Children with Autism: A Parent's Guide, Second Edition. Bethesda, MD: Woodbine House, 28.
- Robbins DI, Fein D, Barton MI, Green JA. (2001). The modified checklist for autism in toddlers: an initial study investigating the early detection of autism and pervasive developmental disorders. Journal of Autism and Developmental Disorders, 31(2): 149-151.
- Research Units on Pediatric Psychopharmacology Network (RUPP) (2002). Risperidone in children with autism and serious behavioral problems. New England Journal of Medicine, 347(5): 314-321.
- Scott FJ, Baron-Cohen S, Bolton P, Brayne C. (2002). The Cast (Childhood Asperger Syndrome Test): preliminary development of a UK screen for mainstream primary-school-age children. Autism, 2(1): 9-31.
- Stone WL, Coonrod EE, Ousley OY. (2000). Brief report: screening tool for autism in two-year-olds (STAT): development and preliminary data. Journal of Autism and Developmental Disorders; 30(6): 607-612.
- Tadevosyan-Leyfer O, Dowd M, Mankoski R, Winklosky B, Putnam S, McGrath L, Tager-Flusberg H, Folstein SE. (2003) A principal components analysis of the autism diagnostic interview-revised. Journal of the American Academy of Child and Adolescent Psychiatry, 42(7): 864-872.
- Van Bourgondien ME, Marcus LM, Schopler E. (1992). Comparison of DSM-III-R and childhood autism rating scale diagnoses of autism. Journal of Autism and Developmental Disorders, 22(4): 493-506.
- Volkmar, F. R. (2000) Medical Problems, Treatments, and Professionals. In: Powers MD, ed. Children with Autism: A Parent's Guide, Second Edition. Bethesda, MD: Woodbine House, 73-74.
- Yeargin-Allsopp M, Rice C, Karapurkar T, Doernberg N, Boyle C, Murphy C. (2003). Prevalence of Autism in a US Metropolitan Area. The Journal of the American Medical Association. Jan 1; 289(1):49-55.