Causes
Causes
| More information about Diagnostic Test/Screeningtools often used with ASD |
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| ADOS |
| ADI-R |
| CHAT |
| MCHAT |
| STAT |
| SCQ |
| CAST |
| ASSQ |
| Autism Spectrum Quotient |
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
- Theory of Mind
- Early Embryogenesis
- Weak Coherence
- Fetal Testosterone Hypothesis
- Oxytocin and AVP
- Abnormal Cellular/Synaptic Growth Hypothesis
- Stimulating Hypothesis
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
