Autism Spectrum Disorders

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Autism Spectrum Disorders
CNP LEVEL: Syndrome



Basic Characteristics

  • Description

Autism Spectrum Disorders is a clinical description of the developmental disorders which are characterized by impaired language development, social development, and learning. According to NIMH estimates, 3.4 out of every 1000 children between 3-10 years of age have one of the disorders in the spectrum.

They include:

  1. Autism
  2. PDD-NOS
  3. Asperger's Syndrome
  4. Rett Syndrome
  5. Childhood Disintegrative Disorder

Children with ASD have extremely delayed development. Symptoms of this disorder usually start to appear between 12 to 36 months and consist of not reaching normal development benchmarks such as babbling by 12 months, speaking by 16 months, or a gradual loss of language or social skills. All children with ASD show deficits in social interactions, verbal and nonverbal communication. They may also show repetitive behaviors and interests, or aggressive behavior.

Those who have ASD have identifiable core deficits recognized by scientists and clinicians.

  1. Core Deficit of Joint Attention
  2. Core Deficit of Social Communication
  3. Repetitive Behavior

Some also argue that those with ASD also have deficits in Visual Perception.


Although all children with ASD show similar deficits, the depth of these deficits can range drastically. Some have very mild deficits like in Asperger's Syndrome, where children have high levels of vocabulary and language skills. Others may have little to no spoken language functionality. Additionally, there are many syndromes and behaviors that display a high comorbidity with ASD, including:

  1. Tantrums and Aggressive Behavior
  2. Epilepsy
  3. Sleep Disorders
  4. Attention Deficit Hyperactivity Disorder
  5. Macrocephaly

More information about Diagnostic Test/Screening tools often used with ASD

ADOSADI-RCHATMCHATSTATSCQCASTASSQ
  • History

Prior to the 1970's, many people thought Autism Spectrum Disorders were a result of psychological causes, such as having an aloof mothering style. However, during the 1980's people began to note that chromosomal disorders and rare syndromes often co-occurred with ASD. As a result, people began to suspect that ASD could have genetic underpinnings. These suspicions were confirmed when, after the development of the ADI-R and ADOS as diagnostic tools and other technical advances, the first candidate gene association and resequencing studies, followed by whole-genome linking studies were done in the late 1990's. These studies were used to identify loci of potential interest.

Causes

Scientists have not found the exact cause of ASD, although all would agree that there is a genetic basis. Strong genetic factors have been found for some of these disorders such as in Rett Syndrome, and there are simple tests for diagnostic purposes for these disorders.

The difficulty in finding the cause of ASD partially lies in its definition, and partially on the complex interplay between genes that happens during development. ASD, like most other behavioral disorders, is diagnosed based off of observable characteristics of the child. However, these diagnosis offer no direction as to which specific genes are defective. Furthermore, two patients with ASD can present very similar symptoms and yet have different defective genes or causes. For example, Rett Syndrome is caused by mutations in the gene MeCP2 while Tuberous Sclerosis is caused by mutations in TSC1 and TSC2. It should be noted that both Rett Syndrome and Tuberous Sclerosis are very rare. It may be that there are certain genes which are more susceptible to environmental influences. If these environmental triggers are there, then the child will develop specific ASD phenotypes, such as a poor language development.9

There are many theories for the cause of ASD. Some include the

  1. Theory of Mind
  2. Simulation of Systems
  3. Weak Coherence
  4. Fetal Testosterone Hypothesis
  5. Oxytocin and AVP
  6. Abnormal Cellular/Synaptic Growth Hypothesis
  7. Stimulating Hypothesis
  8. Abnormal Cellular/Synaptic Growth Hypothesis

Treatments

There are no drugs that can “cure” ASD. There are a variety of treatments available which aim to improve social and communication skills. Because of the complexity of ASD, there is no one treatment that works equally well for all people with ASD. Some common treatments options are:

Applied Behavior Analysis interventionsJoint Attention interventionsTEACCHPivotal Response Treatment

Some clinicians may prescribe medications to target certain symptoms.

There are also many controversial treatments.



External Resources

  • Database links

Citations

1. Keysers, Christian and Valeria Gazzola. Integrating simulation and theory of mind: from self to social cognition. Trends in Cognitive Sciences. Vol 11:5 pg. 194-6; 2007 PMID 17344090

2. Bookheimer, S.Y. et. al. Frontal contributions to face processing differences in autism: Eviedence from fMRI of inverted face processing. "Journal of the International Neuropsychological Society". Cambridge University Press:14:922-32;2008 PMID 18954473

3. Uddin et. al. Neural Basis of Self and Other Representation in Autism: An fMRI Study of Self-Face Recognition. PLoS ONE. 2008;3(10):e3526. Epub 2008 Oct 29 PMID 18958161

4. Jones, J.R. et. al. Hypothesis: Dysregulation of Methylation of Brain-Expressed Genes on the X Chromosome and Autism Spectrum Disorders. American Journal of Medical Genetics Part A 146A:2213-2220 (2008). PMID 18698615

5. Lush, Molly et. al. Current Developments in the Genetics of Autism: From Phenome to Genome. J Neuropathol Exp Neurol. 2008 September; 67(9):829-837. PMID 18716561

6. Arking DE et. al. A common genetic variant in the neurexin superfamily member CNTNAP2 increases familial risk of autism. Am J Hum Genet 2008;82:160-64. PMID 18179894

7. Cook, E.H. and S. W. Scherer. Copy-number variations associated wtih neuropsychiatric conditions. Nature.2008 October;455(16) 919-23. PMID 18923514

8. Gilbert, S.J. et. al. Abnormal functional specialization within medial prefrontal cortex in high-functioning autism: a multi-voxel similarity analysis. Brain: 2009(1). PMID 19174370

9. Grandgeorge, Marine et. al. Environmental Factors Influence Language Development in Children with Autism Spectrum Disorders. PLoS ONE. 2009;4(4):e4683. Epub 2009 Apr 9 PMID 19357766

10. Happe, F. and Uta Frith. The Weak coherence Account: Detail-focused Cognitive Style in Autism Spectrum Disorders. J Autism Dev Disord. 2006 Jan;36(1):5-25. PMID 16450045

11. Schmitz C. Autism: neuropathology, alterations of the GABAergic system, and animal models.Int Rev Neurobiol. 2005;71:1-26. PMID 16512344