Is autism and Asperger's syndrome caused by genetics or some other factor such as the environment?

I am aware about the Neanderthal Theory of autism, Asperger and ADHD, but am not interested in this due to it appearing too broad and to me seems based off of opinions like preferring the cold to the heat which is not always the case, a the term "lack of social life" seem's very broad and not clear nor specific in the aspects of socializing that they are not good with. The aspect of having big brains is also very broad and does not cover in any detail about what it means by that, however if it means intelligence then this is a development from back when we needed to hunt for food as we started to create things and fleeing particular pray on sight became instinct. The section about being meat eaters does not conclude anything as many autistic people are vegans the same as neurotypicals so does not lead us anywhere. The section about woman being more submissive sexually is also not conclusive as most autistic people are asexual so there is no real dominance by both genders as most do not even partake in sexual activities. The graphs included are also questionable as they all seem to be in favor for aspies as they score higher on everything which i would say for things like the chances of having OCD they would be very much correct as the chances of having this when on the spectrum is 40 times more likely. A lack of organization is mentioned which to me does not seem right i feel that we over plan and organize. These category's specified do not cover everyone on the spectrum so therefore is not conclusive.


2 Answers 2


In light of a recent question in MedicalSciences.SE, I thought I would update this answer to include some information from my answer there.

Autism spectrum disorder (ASD) now affects one in 68 births in the United States and is the fastest growing neurodevelopmental disability worldwide (Edmiston, et al. 2017) [free access paper with links to cited papers].

Alarmingly, for the majority of cases, the causes of ASD are largely unknown, but it is becoming increasingly accepted that ASD is no longer defined simply as a behavioral disorder, but rather as a highly complex and heterogeneous biological disorder (Edmiston, et al. 2017).

With information available, the genetic and environmental causes of Autism is open to speculation and interpretation.

The NHS webpage on Autism states (Emphasis mine)

Most researchers believe that certain genes a child inherits from their parents could make them more vulnerable to developing ASD.

Cases of ASD have been known to run in families. For example, younger siblings of children with ASD can also develop the condition, and it's common for identical twins to both develop ASD.

No specific genes linked to ASD have been identified, but it may be a presenting feature of some rare genetic syndromes, including Fragile X syndrome, Williams syndrome and Angelman syndrome.

On environmental causes the NHS say that

Some researchers believe that a person born with a genetic vulnerability to ASD only develops the condition if they're exposed to a specific environmental trigger.

Possible triggers include being born prematurely (before 35 weeks of pregnancy), or being exposed in the womb to alcohol or to certain medication, such as sodium valproate (sometimes used to treat epilepsy during pregnancy).

No conclusive evidence has been found linking pollution or maternal infections in pregnancy with an increased risk of ASD.

Research Autism has some referenced information on leading research into the causes of Autism from the Medical Research Council, National Autistic Society and the Autism Society of America; and the crux of the matter from what is said here is that the causes are still being investigated and

There is no known single cause for autism, but it is generally accepted that it is caused by abnormalities in brain structure or function

The site also provides a list of publications on the possible causes of Autism

There has been research into autoimmune disorders causing ASD.

Edmiston, et al. (2017) stated (emphasis mine):

there are likely multiple, biologically defined subgroups within the ASD spectrum(3–7). Specifically, there is growing evidence that supports maternal immune dysfunction may underlie the behavioral abnormalities observed in a subset of children affected with the disorder(8). Several immunologic risk factors have been described including: genetic associations with immune-related genes(9–16), family history of autoimmune disease(15, 17–21), maternal inflammation and infection during pregnancy(22–27), and altered immune responses in the children, and are associated with increased impairments in core and associated features of ASD(28). More specific to this review, maternal anti-brain autoantibodies, which are thought to access the fetal compartment during gestation, have been identified as one risk factor for developing ASD and are proposed to contribute to early neurodevelopmental perturbations in the developing fetus(29–31).


  1. Lord C, Risi S, Lambrecht L, Cook EH, Leventhal BL, DiLavore PC, et al. 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. 2000;30:205–223.
  2. Newschaffer CJ, Croen La, Daniels J, Giarelli E, Grether JK, Levy SE, et al. The epidemiology of autism spectrum disorders. Annual review of public health. 2007;28:235–258.
  3. Snow AV, Lecavalier L, Houts C. The structure of the Autism Diagnostic Interview-Revised: diagnostic and phenotypic implications. Journal of child psychology and psychiatry, and allied disciplines. 2009;50:734–742.
  4. Ousley O, Cermak T. Autism spectrum disorder: Defining dimensions and subgroups. Current Developmental Disorders Reports. 2013;1:20–28.
  5. McDougle CJ, Landino SM, Vahabzadeh A, O’Rourke J, Zurcher NR, Finger BC, et al. Toward an immune-mediated subtype of autism spectrum disorder. Brain Research. 2015;1617:72–92.
  6. Onore C, Careaga M, Ashwood P. The role of immune dysfunction in the pathophysiology of autism. Brain, Behavior, and Immunity. 2012;26:383–392.
  7. Warren RP, Singh VK, Cole P, Odell JD, Pingree CB, Warren WL, et al. Increased frequency of the null allele at the complement C4b locus in autism. Clinical & Experimental Immunology. 1991;83:438–440.
  8. Warren RP, Odell JD, Warren WL, Burger RA, Maciulis A, Daniels WW, et al. Strong association of the third hypervariable region of HLA-DRβ1 with autism. Journal of Neuroimmunology. 1996;67:97–102.
  9. Torres AR, Sweeten TL, Cutler A, Bedke BJ, Fillmore M, Stubbs EG, et al. The association and linkage of the HLA-A2 class I allele with autism. Human immunology. 2006;67:346–351.
  10. Campbell DB, Li C, Sutcliffe JS, Persico AM, Levitt P. Genetic evidence implicating multiple genes in the MET receptor tyrosine kinase pathway in autism spectrum disorder. Autism Research. 2008;1:159–168.
  11. Thanseem I, Nakamura K, Miyachi T, Toyota T, Yamada S, Tsujii M, et al. Further evidence for the role of MET in autism susceptibility. Neuroscience Research. 2010;68:137–141.
  12. Mostafa GA, Shehab AA. The link of C4B null allele to autism and to a family history of autoimmunity in Egyptian autistic children. Journal of Neuroimmunology. 2010;223:115–119.
  13. Jung JY, Kohane IS, Wall DP. Identification of autoimmune gene signatures in autism. Translational psychiatry. 2011;1:e63–e63.
  14. Torres AR, Westover JB, Gibbons C, Johnson RC, Ward DC. Activating killer-cell immunoglobulin-like receptors (KIR) and their cognate HLA ligands are significantly increased in autism. Brain, behavior, and immunity. 2012;26:1122–1127.
  15. Comi AM, Zimmerman AW, Frye VH, Law PA, Peeden JN. Familial Clustering of Autoimmune Disorders and Evaluation of Medical Risk Factors in Autism. Journal of Child Neurology. 1999;14:388–394.
  16. Atladóttir HO, Pedersen MG, Thorsen P, Mortensen PB, Deleuran B, Eaton WW, et al. Association of family history of autoimmune diseases and autism spectrum disorders. Pediatrics. 2009;124:687–694.
  17. Vinet É, Pineau CA, Clarke AE, Scott S, Fombonne É, Joseph L, et al. Increased Risk of Autism Spectrum Disorders in Children Born to Women With Systemic Lupus Erythematosus: Results From a Large Population-Based Cohort. Arthritis & rheumatology (Hoboken, NJ) 2015;67:3201–3208.
  18. Wu S, Ding Y, Wu F, Li R, Xie G, Hou J, et al. Family history of autoimmune diseases is associated with an increased risk of autism in children: A systematic review and meta-analysis. Neuroscience and biobehavioral reviews. 2015;55:322–332.
  19. Chen S-W, Zhong X-S, Jiang L-N, Zheng X-Y, Xiong Y-Q, Ma S-J, et al. Maternal autoimmune diseases and the risk of autism spectrum disorders in offspring: A systematic review and meta-analysis. Behavioural brain research. 2016;296:61–69.
  20. Chess S. Autism in children with congenital rubella. Journal of autism and childhood schizophrenia. 1971;1:33–47.
  21. Meyer U, Nyffeler M, Engler A, Urwyler A, Schedlowski M, Knuesel I, et al. The time of prenatal immune challenge determines the specificity of inflammation-mediated brain and behavioral pathology. The Journal of neuroscience : the official journal of the Society for Neuroscience. 2006;26:4752–4762.
  22. Smith SEP, Li J, Garbett K, Mirnics K, Patterson PH. Maternal Immune Activation Alters Fetal Brain Development through Interleukin-6. The Journal of neuroscience : the official journal of the Society for Neuroscience. 2007;27:10695–10702.
  23. Atladóttir HÓ, Thorsen P, Østergaard L, Schendel DE, Lemcke S, Abdallah M, et al. Maternal Infection Requiring Hospitalization During Pregnancy and Autism Spectrum Disorders. Journal of Autism and Developmental Disorders. 2010;40:1423–1430.
  24. Patterson PH. Maternal infection and immune involvement in autism. Trends in Molecular Medicine. 2011;17:389–394.
  25. Garay PA, Hsiao EY, Patterson PH, McAllister AK. Brain, Behavior, and Immunity Maternal immune activation causes age- and region-specific changes in brain cytokines in offspring throughout development. 2012
  26. Ashwood P, Van de Water J. Is autism an autoimmune disease? Autoimmunity reviews. 2004;3:557–562.
  27. Braunschweig D, Van de Water J. Maternal autoantibodies in autism. Archives of neurology. 2012;69:693–699.
  28. Fox E, Amaral D, Van de Water J. Maternal and fetal antibrain antibodies in development and disease. Developmental Neurobiology. 2012;72:1327–1334.
  29. Fox-Edmiston E, Van De Water J. Maternal Anti-Fetal Brain IgG Autoantibodies and Autism Spectrum Disorder: Current Knowledge and its Implications for Potential Therapeutics. CNS Drugs. 2015;29:715–724.

In conclusion, they pointed out that Maternal autoantibody related (MAR) ASD:

has been noted by numerous researchers describing the presence of maternal autoantibodies reactive to fetal brain proteins in a subset of mothers of children with ASD. Further, there is now an abundance of evidence supporting their deleterious role in neurodevelopment. For the most part, these studies have described similar experimental outcomes and, given the clinical and biological heterogeneity of ASD, there likely exists a complex relationship between the presence of maternal anti-fetal brain antibodies and developmental trajectory of exposed offspring. It is still unclear how and when these maternal autoantibodies arise, but studies currently underway may provide increased insight into their ontogeny.


Edmiston, E., Ashwood, P., & Van de Water, J. (2017). Autoimmunity, autoantibodies, and autism spectrum disorder. Biological psychiatry, 81(5), 383-390. Pubmed Central: PMC5373490

  • $\begingroup$ thanks for the answer that's interesting and until i physically look into it a lot more i wont know exactly how it is developed. i mean the reason i think its genetics is because of it running in my family appearing to get less mild as we go down the generations so from nothing in my parents to me with Asperger's syndrome, then my sister who is slightly further along the spectrum, then my brother who is the furthest of us along the spectrum, this is also true for all of my cousins. $\endgroup$
    – matt mods
    Aug 9, 2017 at 15:08
  • $\begingroup$ @mattmods - this is the problem highlighted in my answer. Nobody knows the definitive answer to how Autism develops, however the situation you describe with your family line is known to happen, again as indicated. Let's hope they find the answer soon $\endgroup$ Aug 9, 2017 at 19:37
  • $\begingroup$ Yeah I mean I know it's quite a common pattern and such but let's just hope they find the cause soon or if not it gives me a reason to go into neuroscience I guess. $\endgroup$
    – matt mods
    Aug 9, 2017 at 21:25
  • $\begingroup$ Especially the genetic region on 15q is very unstable due to many DNA low copy repeats (Prader-Willi and Angelmann are macrodeletions on that arm of the chromosome). A few gene locations there have been associated with autism (among patients with a deletion in that area there is a higher prevalence of autism spectrum disorder). I would say that there undeniably exist a correlation between gene polymorphisms and autism, but the causative role and the extent remains unclear. This is a very active field of researchy $\endgroup$
    – Narusan
    Sep 2, 2019 at 17:08

Since the 1970s, researchers have found out and known that genes make a contribution to the pervasive developmental disorder or autism when two identical twins have shared a similar condition.

As the world progresses, scientists have found out the variety of genetic changes in the DNA that contribute to the autism spectrum. However, genetics cannot be solely accounted for the risks of developing signs for autism spectrum. There are various other factors involved as well,

  • A child being born to older parents
  • Low birth weight and premature infants
  • Hormonal and metabolic imbalances
  • Fetal exposures to the medications such as valproic acid or thalidomide
  • Exposure to heavy metals and environmental toxins
  • Fragile X syndrome and other inherited disorders
  • Having an immediate family member with autism

Working with Arizona Centers for Comprehensive Education and Life Skills, I have realized children or adults with pervasive spectrum need distinctive care and affection.

  • 1
    $\begingroup$ Welcome to psych.SE! Your answer would be much more useful with citations for the factors you mention, both so that the original questioner has a way to find more information and so that all your readers know what technical perspective you're speaking from. $\endgroup$
    – Krysta
    Nov 27, 2018 at 14:12

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