Causes of autism

Brain sections and how autism relates to them

Many causes of autism, including environmental and genetic factors, have been recognized or proposed, but understanding of the theory of causation of autism is incomplete.[1] Attempts have been made to incorporate the known genetic and environmental causes into a comprehensive causative framework.[2] ASD (autism spectrum disorder) is a neurodevelopmental disorder marked by impairments in communicative ability and social interaction, as well as restricted and repetitive behaviors, interests, or activities not suitable for the individual's developmental stage. The severity of symptoms and functional impairment vary between individuals.[3]

There are many known environmental, genetic, and biological causes of autism. Research indicates that genetic factors predominantly contribute to its appearance. The heritability of autism is complex and many of the genetic interactions involved are unknown.[1] In rare cases, autism has been associated with agents that cause birth defects.[4] Many other causes have been proposed.

Different underlying brain dysfunctions have been hypothesized to result in the common symptoms of autism, just as completely different brain types result in intellectual disability.[1][5] In recent years, the prevalence and number of people diagnosed with the disorder have increased dramatically. There are many potential reasons for this occurrence, particularly the changes in the diagnostic criteria for autism.[6]

Environmental factors that have been claimed to contribute to autism or exacerbate its symptoms, or that may be important to consider in future research, include certain foods,[7] infectious disease, heavy metals, solvents, diesel exhaust, PCBs, phthalates and phenols used in plastic products, pesticides, brominated flame retardants, alcohol, smoking, and illicit drugs.[6] Among these factors, vaccines have attracted much attention, as parents may first become aware of autistic symptoms in their child around the time of a routine vaccination, and parental concern about vaccines has led to a decreasing uptake of childhood immunizations and an increasing likelihood of measles outbreaks.[8][9] Overwhelming scientific evidence shows no causal association between the measles-mumps-rubella (MMR) vaccine and autism. Although there is no definitive evidence that the vaccine preservative thimerosal causes autism, studies have indicated a possible link between thimerosal and autism in individuals with a hereditary predisposition for autoimmune disorders.[10][11] In 2007, the Center for Disease Control stated there was no support for a link between thimerosal and autism, citing evidence from several studies, as well as a continued increase in autism cases following the removal of thimerosal from childhood vaccines.[12]

  1. ^ a b c Waye MM, Cheng HY (April 2018). "Genetics and epigenetics of autism: A Review". Psychiatry and Clinical Neurosciences (Review). 72 (4): 228–244. doi:10.1111/pcn.12606. eISSN 1440-1819. PMID 28941239. S2CID 206257210.
  2. ^ Sarovic D (November 2021). "A Unifying Theory for Autism: The Pathogenetic Triad as a Theoretical Framework". Frontiers in Psychiatry (Review). 12: 767075. doi:10.3389/fpsyt.2021.767075. PMC 8637925. PMID 34867553. S2CID 244119594.
  3. ^ American Psychiatric Association (2022). Diagnostic and statistical manual of mental disorders: DSM-5-TR (5th ed.). American Psychiatric Association Publishing. doi:10.1176/appi.books.9780890425787. ISBN 978-0-89042-575-6. S2CID 249488050.
  4. ^ Arndt TL, Stodgell CJ, Rodier PM (2005). "The teratology of autism". International Journal of Developmental Neuroscience (Review). 23 (2–3): 189–199. doi:10.1016/j.ijdevneu.2004.11.001. PMID 15749245. S2CID 17797266.
  5. ^ Hodges H, Fealko C, Soares N (February 2020). "Autism spectrum disorder: definition, epidemiology, causes, and clinical evaluation". Translational Pediatrics. 9 (Suppl 1): S55–S65. doi:10.21037/tp.2019.09.09. PMC 7082249. PMID 32206584.
  6. ^ a b Salari N, Rasoulpoor S, Rasoulpoor S, Shohaimi S, Jafarpour S, Abdoli N, et al. (July 2022). "The global prevalence of autism spectrum disorder: a comprehensive systematic review and meta-analysis". Italian Journal of Pediatrics. 48 (1): 112. doi:10.1186/s13052-022-01310-w. PMC 9270782. PMID 35804408.
  7. ^ Quan J, Panaccione N, King JA, Underwood F, Windsor JW, Coward S, et al. (March 2019). "A257 Association Between Celiac Disease and Autism Spectrum Disorder: A Systematic Review". Journal of the Canadian Association of Gastroenterology. 2 (Supplement_2): 502–503. doi:10.1093/jcag/gwz006.256. ISSN 2515-2084. PMC 6512700.
  8. ^ Wilder-Smith AB, Qureshi K (March 2020). "Resurgence of Measles in Europe: A Systematic Review on Parental Attitudes and Beliefs of Measles Vaccine". Journal of Epidemiology and Global Health. 10 (1): 46–58. doi:10.2991/jegh.k.191117.001. PMC 7310814. PMID 32175710.
  9. ^ Gidengil C, Chen C, Parker AM, Nowak S, Matthews L (October 2019). "Beliefs around childhood vaccines in the United States: A systematic review". Vaccine. 37 (45): 6793–6802. doi:10.1016/j.vaccine.2019.08.068. PMC 6949013. PMID 31562000.
  10. ^ Di Pietrantonj C, Rivetti A, Marchione P, Debalini MG, Demicheli V, et al. (Cochrane Acute Respiratory Infections Group) (November 2021). "Vaccines for measles, mumps, rubella, and varicella in children". The Cochrane Database of Systematic Reviews. 2021 (11): CD004407. doi:10.1002/14651858.CD004407.pub5. PMC 8607336. PMID 34806766.
  11. ^ Kern JK, Geier DA, Mehta JA, Homme KG, Geier MR (December 2020). "Mercury as a hapten: A review of the role of toxicant-induced brain autoantibodies in autism and possible treatment considerations". Journal of Trace Elements in Medicine and Biology. 62: 126504. Bibcode:2020JTEMB..6226504K. doi:10.1016/j.jtemb.2020.126504. PMID 32534375. S2CID 219468115.
  12. ^ "Timeline: Thimerosal in Vaccines (1999-2010)". CDC. 19 August 2020. Retrieved 2024-04-24.