Autism classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Classification
Autism is a brain development disorder that first gives signs during infancy or childhood and follows a steady course without remission or relapse. Impairments result from maturation-related changes in various systems of the brain. Autism is one of the five pervasive developmental disorders (PDD), which are characterized by widespread abnormalities of social interactions and communication, and severely restricted interests and highly repetitive behavior.
Of the other four PDD forms, Asperger syndrome is closest to autism in signs and likely causes; Rett syndrome and childhood disintegrative disorder share several signs with autism, but may have unrelated causes; PDD not otherwise specified (PDD-NOS) is diagnosed when the criteria are not met for a more specific disorder.[1] Unlike autism, Asperger's has no substantial delay in language development.[2] The terminology of autism can be bewildering, with autism, Asperger's and PDD-NOS often called the autism spectrum disorders (ASD) or sometimes the autistic disorders,[3] whereas autism itself is often called autistic disorder, childhood autism, or infantile autism. In this article, autism refers to the classic autistic disorder, while other sources sometimes use autism or the autisms to refer to ASD,[4] or equate ASD with PDD. 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.[5]
The manifestations of autism cover a wide spectrum, ranging from individuals with severe impairments—who may be silent, mentally disabled, and locked into hand flapping and rocking—to less impaired individuals who may have active but distinctly odd social approaches, narrowly focused interests, and verbose, pedantic communication.[6] Sometimes the syndrome is divided into low-, medium- and high-functioning autism (LFA, MFA, and HFA), based on IQ thresholds, or on how much support the individual requires in daily life; these subdivisions are not standardized and are controversial. Autism can also be divided into syndromal and non-syndromal autism, where the former is associated with severe or profound mental retardation or a congenital syndrome with physical symptoms, such as tuberous sclerosis.[7] Although individuals with Asperger's tend to perform better cognitively than those with autism, the extent of the overlap between Asperger's, HFA, and non-syndromal autism is unclear.[8]
Some studies have reported diagnoses of autism in children due to a loss of language or social skills after 14 months of age, as opposed to a failure to make progress. Several terms are used for this phenomenon, including regressive autism, setback autism, and developmental stagnation. The validity of this distinction remains controversial; it is possible that regressive autism is a specific subtype.[9]
The inability to identify biologically meaningful subpopulations has hampered research into causes.[10] It has been proposed to classify autism using genetics as well as behavior, with the name Type 1 autism denoting rare autism cases that test positive for a mutation in the gene contactin associated protein-like 2 (CNTNAP2).[11]
References
- ↑ Lord C, Cook EH, Leventhal BL, Amaral DG (2000). "Autism spectrum disorders". Neuron. 28 (2): 355–63. doi:10.1016/S0896-6273(00)00115-X. PMID 11144346.
- ↑ American Psychiatric Association (2000). "Diagnostic criteria for 299.80 Asperger's Disorder (AD)". Diagnostic and Statistical Manual of Mental Disorders (4th ed., text revision (DSM-IV-TR) ed.). ISBN 0890420254.
- ↑ Freitag CM (2007). "The genetics of autistic disorders and its clinical relevance: a review of the literature". Mol Psychiatry. 12 (1): 2–22. doi:10.1038/sj.mp.4001896. PMID 17033636.
- ↑ Geschwind DH, Levitt P (2007). "Autism spectrum disorders: developmental disconnection syndromes". Curr Opin Neurobiol. 17 (1): 103–11. doi:10.1016/j.conb.2007.01.009. PMID 17275283.
- ↑ Piven J, Palmer P, Jacobi D, Childress D, Arndt S (1997). "Broader autism phenotype: evidence from a family history study of multiple-incidence autism families" (PDF). Am J Psychiatry. 154 (2): 185–90. PMID 9016266.
- ↑ Happé F (1999). "Understanding assets and deficits in autism: why success is more interesting than failure" (PDF). Psychologist. 12 (11): 540–7.
- ↑ Cohen D, Pichard N, Tordjman S; et al. (2005). "Specific genetic disorders and autism: clinical contribution towards their identification". J Autism Dev Disord. 35 (1): 103–16. doi:10.1007/s10803-004-1038-2. PMID 15796126.
- ↑ Validity of ASD subtypes:
- Klin A (2006). "Autism and Asperger syndrome: an overview". Rev Bras Psiquiatr. 28 (suppl 1): S3–S11. doi:10.1590/S1516-44462006000500002. PMID 16791390.
- Witwer AN, Lecavalier L (2008). "Examining the validity of autism spectrum disorder subtypes". J Autism Dev Disord. doi:10.1007/s10803-008-0541-2. PMID 18327636.
- ↑ Volkmar F, Chawarska K, Klin A (2005). "Autism in infancy and early childhood". Annu Rev Psychol. 56: 315–36. doi:10.1146/annurev.psych.56.091103.070159. PMID 15709938. A partial update is in: Volkmar FR, Chawarska K (2008). "Autism in infants: an update". World Psychiatry. 7 (1): 19–21. PMC 2366821. PMID 18458791.
- ↑ Altevogt BM, Hanson SL, Leshner AI (2008). "Autism and the environment: challenges and opportunities for research". Pediatrics. 121 (6): 1225–9. doi:10.1542/peds.2007-3000. PMID 18519493.
- ↑ Stephan DA (2008). "Unraveling autism". Am J Hum Genet. 82 (1): 7–9. doi:10.1016/j.ajhg.2007.12.003. PMID 18179879.