Over the last decade many have asked what the cause has been in the increase of autism. Some of the problem in answering the question arises from the question itself. Too often we look for an explicit cause of something, for example the rise in autism, when there may not be a cause. It is more likely that there are a number of intervening variables which have fed what many consider a substantial rise in the number or percentage of children with the disorder. (I added “many consider” to the previous sentence because there are some who do not believe there is an actual substantial increase in the occurrence of the disorder, only the diagnosis. Some of the articles referenced below will share this differing point of view.)
So, what are some of the intervening variables that appear to have an effect on the rise of autism?
Age of Parents
Fairly recent research has shown a strong correlation between the age of the parents (father and/or mother) and an increased risk of a child being born with autism. As one article states: “Advanced maternal and paternal ages are independently associated with ASD risk.” (a) Are more parents waiting until they are older to have children?
Genetics
It’s commonly understood that genetics play a significant role in many if not most cases of autism. (b)
One or Two Parents with Mild Autistic like Symptoms
This is sometimes seen in parents who are in certain professional fields. (c) When both parents are in these fields, sometimes referred to as systemizing fields, the chances of having a child with autism increase even further. Are more parents working and finding success in these fields than in the past? Are more of these parents meeting others with similar “systemizing” characteristics, and having children together? (see: Empathizing–systemizing theory: http://en.wikipedia.org/wiki/Empathizing%E2%80%93systemizing_theory)
“This is sometimes seen in parents who are in professional fields such engineering, computer science, and accounting. “Experts are becoming increasingly concerned that engineers, scientists and computer programmers who meet their partners at work may be fuelling an increase in cases of autism.” (c.1)
Lack of Prenatal Vitamins
A number of research articles have demonstrated a correlation between the lack of some prenatal vitamins and a higher occurrence of Autism. One of these is vitamin D (d), possibly due to greater levels of pollution and fewer hours under the sun. Other vitamins include the folic acids. (d.1.)
Pollution and Toxic Substances (possibly both internal and external) (d)
A number of studies have demonstrated a correlation between the increase of certain pollutants, to include mercury, and possibly other pollutants found close to a busy freeway (e), and higher incidences of autism. There may be a correlation between higher incidences of autism and other pollutants as well.
Better Identification
Better tools and awareness as well as training and expertise have resulted in more children being diagnosed earlier and more correctly. Logically there have been children who may have previously been diagnosed with another disorder, such as a language disorder, and who are now being diagnosed with Autism. (f)
Broader Categorization
This now includes Aspergers (Asbergers) as well as a spectrum disorder, PDD NOS. Many children are diagnosed today, to be found within the autism spectrum who would not have been fifteen, ten, or even five years ago. (g) Some studies have demonstrated that 25% of the increase of autism spectrum diagnoses in California to be correlated with changes in diagnostic criteria. (g.1)
Over Identification
There have always been “popular” diagnoses. ADHD recently when through that phase with a significantly higher percentage of children being diagnosed in the US than Europe. There is a great deal of anecdotal evidence of parents telling their doctor that they think (or know) their child has autism and receiving the diagnosis from the doctor. There has also been a study showing that there is a increased chance of a child receiving the diagnosis when the parent knows another parent with a child with autism. There could be a number of causes for this; however, the study believes the result is over identification. (h)
Diseases
Doctors have found a connection between some mothers who have contracted Lyme disease before or during pregnancy and autism in their children. Though this represents a very small number of children, it may have an impact on some and the treatment of the Lyme disease seems to alleviate the autistic symptoms in the child. (i) There is also a correlation in some cases between prenatal difficulties to include maternal infection and autism.
Gastrointestinal (j)
Other Variables
There are a number of additional variables which while they too are probably not causes of autism, they may have an impact on the child’s development of the disorder.
While the actual percentage of children being diagnosed with an autism spectrum disorder has increased dramatically, some, perhaps as many as 25% (as demonstrated in some California studies) of the increase is due to changing diagnostic criteria as well as inaccurate diagnoses. This still leaves a substantial increase in the percentage of children with an accurate diagnosis and the corresponding needs for intervention. This is probably due to a combination of risk factors as noted above.
References: With opposing points of view.
Study Fails To Establish Diagnostic Substitution as a Factor in Increased Rate of Autism
http://pharmacotherapyjournal.org/doi/abs/10.1592/phco.24.8.812.36060?journalCode=phco
What's going on? The question of time trends in autism.
http://www.blogger.com/goog_663558501
(a) Maternal and Paternal Age and Risk of Autism Spectrum Disorders
http://archpedi.ama-assn.org/cgi/content/abstract/161/4/334
(b) The Increase in Autism Diagnoses: Two Hypotheses
http://www.sciencebasedmedicine.org/index.php/the-increase-in-autism-diagnoses-two-hypotheses/
(b) Advances in autism genetics: on the threshold of a new neurobiology
http://www.nature.com/nrg/journal/v9/n5/full/nrg2346.html
(b) The Genetics of Autism
http://pediatrics.aappublications.org/content/113/5/e472.short
(c.1) Couple who meet at work have autistic babies?
http://timesofindia.indiatimes.com/life-style/health-fitness/health/Couple-who-meet-at-work-have-autistic-babies/articleshow/10829638.cms
(c) Do Tech-Rich Regions Have More Autism?
http://blogs.wsj.com/ideas-market/2011/06/21/do-tech-rich-regions-have-more-autism/?mod=google_news_blog
(c) Are Autism Spectrum Conditions More Prevalent in an Information-Technology Region? A School-Based Study of Three Regions in the Netherlands
http://www.springerlink.com/content/4n265812pw547773/
(c) Mathematical Talent is Linked to Autism
http://www.springerlink.com/content/21t03377610752g0/
(c) Autism spectrum disorders in relation to parental occupation in technical fields (This article partially contradicts some of the other related articles.)
http://onlinelibrary.wiley.com/doi/10.1002/aur.84/full
(c) The hyper-systemizing, assortative mating theory of autism
http://www.autismresearchcentre.com/docs/papers/2006_BC_Neuropsychophamacology.pdf
(d) Autism and Vitamin D
http://www.sciencedirect.com/science/article/pii/S0306987707005373
(d.1) Prenatal Vitamins, One-carbon Metabolism Gene Variants, and Risk for Autism
http://www.blogger.com/goog_663558526
(d.1) Folic Acid Supplements in Pregnancy and Severe Language Delay in Children
http://jama.ama-assn.org/content/306/14/1566.short
(e) Proximity to point sources of environmental mercury release as a predictor of autism prevalence
http://www.sciencedirect.com/science/article/pii/S1353829208000142
(e) Residential Proximity to Freeways and Autism in the CHARGE Study
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3114825/
(e) Mercury and autism: Accelerating Evidence?
http://www.detoxmetals.com/content/AUTISM%20AND%20Hg/autism_reprint.pdf
(e) Autism Spectrum Disorders and Identified Toxic Land Fills: Co-Occurrence Across States
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3091342/
(e) A Significant Factor in Autism: Methyl Mercury Induced Oxidative Stress in Genetically Susceptible Individuals
http://www.springerlink.com/content/t333806128710n2t/
(a)(b)(e) Contributions of the environment and environmentally vulnerable physiology to autism spectrum disorders
http://journals.lww.com/co-neurology/Abstract/2010/04000/Contributions_of_the_environment_and.4.aspx
(f) Identification and Evaluation of Children With Autism Spectrum Disorders
http://aappolicy.aappublications.org/cgi/content/abstract/pediatrics;120/5/1183
(f) Recent Advances in Early Identification and Treatment of Autism
http://cdp.sagepub.com/content/20/5/335.short
(f) Prospective Identification of Autism Spectrum Disorders in Infancy and Toddlerhood Using Developmental Surveillance: The Social Attention and Communication Study
http://journals.lww.com/jrnldbp/Abstract/2010/06000/Prospective_Identification_of_Autism_Spectrum.3.aspx
(f) Pediatricians’ perspectives on identification and diagnosis of autism spectrum disorders
http://ecr.sagepub.com/content/8/3/254.short
(f) Identification and diagnosis of autism spectrum disorders: an update
http://www.futuremedicine.com/
(g) The increasing prevalence of autism spectrum disorders
http://www.sciencedirect.com/science/article/pii/S1750946710000917
(g) (h) Validity of Three Pervasive Developmental Disorder (PDD) Subtypes— Autistic Disorder, Asperger’s Disorder, and PDD Not Otherwise Specified
http://www.touchpsychiatry.com/articles/validity-three-pervasive-developmental-disorder-pdd-subtypes-autistic-disorder-asperger-s-d?page=0,4
(g.1) Diagnostic change and the increased prevalence of autism
http://ije.oxfordjournals.org/content/38/5/1224.short
(g) (h) Social Influence and the Autism Epidemic
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2927813/
(h) The challenges of diagnosing Autism spectrum disorder in the community
http://gradworks.umi.com/34/81/3481401.html
(h) Stability of Initial Autism Spectrum Disorder Diagnoses in Community Settings
http://www.springerlink.com/content/4k15g10321560507/
(i) Doctors find link between Lyme disease, Autism
http://www.foxnews.com/health/2011/09/27/doctors-find-link-between-lyme-disease-autism/
(i)A Qualitative and Quantitative Review of Obstetric Complications and Autistic Disorder
http://www.springerlink.com/content/b27wwmu86966r987/
(i)Immune involvement in schizophrenia and autism: Etiology, pathology and animal models
http://www.sciencedirect.com/science/article/pii/S0166432808006980
(i) The Time of Prenatal Immune Challenge Determines the Specificity of Inflammation-Mediated Brain and Behavioral Pathology
http://www.jneurosci.org/content/26/18/4752.short
(j) Autism and gastrointestinal symptoms
http://www.springerlink.com/content/h02x77hu54672212/
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