The Rise in Autism and ADHD
The modern world is somehow compromising our children’s brains on an unprecedented scale. One reflection of this is the rapid rise in autism, a developmental disability that used to be incredibly rare.
If you are in your thirties or forties and living in a developed country, there is a very good chance that one of your friends, neighbors, or work colleagues has a child with autism. In our parents’ generation, this would have been unheard of.
The rise in autism is not simply a matter of improved diagnosis. Research shows there has been a true increase in cases—and at an extraordinary rate. In the United States, the number of children diagnosed with autism used to be 1 in 10,000.[i] Now it is 1 in 40.[ii] The odds are even worse for boys, with the latest numbers released from the Centers for Disease Control (CDC) showing that autism will affect 1 in 27 boys born today.[iii]
In parallel, there has also been a troubling rise in attention-deficit/hyperactivity disorder (ADHD), which now affects more than 7 percent of children in the United States.[iv] In 2016, there were more than 5.4 million American children with ADHD, of whom two-thirds were taking medication.[v] And it doesn’t end there. The CDC has reported that the total number of children in the United States with any form of developmental disability, including speech and language impairments, intellectual disabilities, cerebral palsy, and autism, is 1 in 6.[vi]
This is a dire situation that cannot be ignored. There is an urgent need to figure out what is happening—what has changed in recent decades that is compromising the developing minds of so many children? That is a question many researchers have been grappling with and the answer, it seems, is a multifaceted one. There is not one single cause, but a variety of external risk factors that can cause autism, ADHD, and other developmental problems, especially in children who are genetically vulnerable.
The good news is that we have the power to change many of these risk factors. New science is emerging every day that reveals ways to dramatically reduce the risk of developmental disabilities by ensuring adequate nutrients during pregnancy, reducing the risk of preterm birth, and minimizing exposure to toxins. The research is also revealing many common threads that tie together seemingly unrelated threats to infant brain health, as this chapter explains.
Before exploring those common threads, I want to briefly address the argument that autism is not actually caused by factors unique to the modern world, such as toxin exposure, but is instead something that existed throughout human history but simply went unrecognized.
Is There Really an Autism Epidemic?
In his book, Neurotribes: The Legacy of Autism and the Future of Neurodiversity, reporter Steve Silberman argues that autism merely reflects natural variations in the human brain function. “Whatever autism is, it is not a unique product of modern civilization. It is a strange gift from our deep past passed down through millions of years of evolution.”[vii]
Silberman advocates for a view of autism as a type of “neurodiversity” rather than an impairment, noting that “Autistic people, for instance, have prodigious memories for facts, are often highly intelligent in ways that don’t register on verbal IQ tests, and are capable of focusing for long periods on tasks that take advantage of their natural gift for detecting flaws in visual patterns. By autistic standards, the ‘normal’ human brain is easily distractible, is obsessively social, and suffers from a deficit of attention to detail.”
There may be some truth to Silberman’s view, at least for many individuals on the autism spectrum, but to parents of children with more severe forms of autism, this concept of “neurodiversity” is far from reality. As one such parent, J.B. Handley, comments in his book How to End the Autism Epidemic, “I resent the way Mr. Silberman . . . and many neurodiversity advocates are romanticizing a devastating disability.”[viii]
To be diagnosed with autism, a child must show “persistent deficits in social communication and social interaction.”[ix] The severity of language and social impairment can vary widely, with some autistic children being able to communicate well and others not able to speak at all. Other common characteristics include repetitive body movements (such as flapping, rocking, and spinning), unusual interest in specific objects, difficulties with changes in routine, and extreme sensitivity to sensory inputs such as light, sound, taste, and touch. Approximately one-third of children with autism also have significant intellectual disability.
It is perhaps unsurprising then that autism can have far-reaching impacts on a child’s life. In their 2017 book, journalist Dan Olmsted and autism parent Mark Blaxill note that “most with an autism diagnosis will never be employed, pay taxes, fall in love, get married, have children, or be responsible for their health and welfare.”[x] This view is supported by the data.
Research shows that the average cost of supporting an individual with autism over the course of their lifetime is $1.4 million.[xi] Around one-third of children with the disorder are unable to speak, and more than half are prone to physical aggression, with many also hurting themselves.[xii]
In reality, the term “autism” encompasses a wide variety of abilities and challenges. We can acknowledge the extraordinary gifts of many individuals with autism while at the same time recognizing that it is often a serious and lifelong disability that is worth preventing.
The vast weight of scientific evidence suggests that autism is not a natural state of affairs but the result of harm to a developing brain. As you will learn throughout this book, there are many steps we can take to protect a child’s brain health and reduce the odds of developing autism. Silberman’s argument that autism merely reflects natural diversity in human cognitive function “passed down through millions of years of evolution” just does not fit with the facts.
The one grain of truth to this contention is that there is a genetic component to autism. Having a sibling with the disorder is probably the single biggest risk factor.[xiii] But genes alone do not cause autism. Some external triggering factor or combination of factors is required. Simply put, genetics cannot explain why almost 3 percent of boys in the United States today will have autism, whereas before the 1970s, the number was 1 in 10,000. In many countries, the prevalence of autism has increased exponentially in recent years, even though the human gene pool remains much the same.[xiv]
As Handley notes, “Ask any teacher, doctor, nurse, or coach who has been working for three decades or more and you’ll always hear the same thing: something new and very different is happening with children today.”[xv] Even now, the percentage of children with autism continues to rise each year. Specifically, the prevalence of Autism Spectrum Disorder in US children aged three to 17 years was 2.24 percent in 2014, 2.41 percent in 2015, and 2.76 percent in 2016.[xvi]
The rise in autism is particularly troubling when we go further back and graph the number of autism cases by year of birth, as shown in the figure below.
Figure: Prevalence of autism in California by year of birth.[xvii]
This graph shows that autism, which used to be quite rare, has become disturbingly common. We can also see that the inflection point was somewhere around the 1980s, with an exponential rise throughout the subsequent decades.
Some have questioned whether this exponential rise is a true increase in cases, or whether we have simply started categorizing more children as autistic. It is true that the diagnostic criteria have expanded, with the creation of the broader umbrella term “autism spectrum disorder” to capture milder cases and children with Asperger’s Syndrome, for example. In addition, there is likely a greater awareness of the problem amongst parents and doctors, so fewer children go undiagnosed.
These factors may have accounted for a small rise in the prevalence of autism, but nowhere close to the exponential rise that has occurred in the past 30 years. Rigorous studies clearly show that what we now regard as autism was exceedingly rare before the 1980s.[xviii]
The fact is that we are facing an unprecedented increase in autism and other developmental problems. According to Dr. Cynthia Nevison, an environmental researcher at the University of Colorado, approximately 75 to 80 percent of the increase since 1988 is due to an actual increase in the disorder rather than changes in how autism is diagnosed.[xix]
Perhaps the most concerning feature of the autism prevalence data is that it appears we have not yet reached “peak autism.” At the time of writing, the percentage of children diagnosed with autism continues to climb. Simultaneously, we are also witnessing a rise in other neurological and behavioral disorders that reflect problems with early brain development, particularly attention-deficit/hyperactivity disorder (ADHD).
The prevalence of ADHD has not been rising as quickly as autism, but it affects far more children. It is the most common developmental disorder, now impacting at least 7 percent of children in the United States.
Children with ADHD will typically have difficulty staying focused and paying attention. They may also have greater difficulty regulating their own behavior or emotional state. In practice, this may lead to hyperactive, impulsive, and aggressive behavior. By some estimates, more than half of children with ADHD will display significant aggressive behavior.[xx] As we might expect, this has been found to severely limit a child’s ability to build friendships and succeed in school.[xxi]
Common Threads Underlying Autism and ADHD
The explosion in the number of children facing developmental disorders has fortunately sparked a flurry of scientific research to try to find the possible causes. Much of the funding has been devoted to research studying possible genetic causes, which in some ways makes sense, given that autism often runs in families. Yet understanding the genetic contributors will take us only so far. Our genes have not changed dramatically in the past 30 years, yet the number of children with autism has.
Clearly the exponential rise is not the result of genetics but some external factor in the world around us or, more likely, a combination of factors. Some of the genes involved in autism could just make some children more vulnerable to those external factors.
To start unraveling the mystery of what is causing the rise in autism, the most logical starting point is to consider potential risk factors that have changed the most since the early 1980s, when autism rates began to rise exponentially. This suggests several possibilities, including
- a rise in autoimmune and inflammatory conditions amongst pregnant women.
- an increase in the number of people having children later in life.
- an expansion of the newborn vaccine schedule, resulting in very young babies receiving a much higher dose of aluminum.
- replacing aspirin with acetaminophen (also known as Tylenol/Panadol) as the pain and fever medicine of choice in babies.
- an increase in the use of pesticides on food crops.
- an increase in exposure to flame-retardant chemicals.
For some of these possibilities, the link with autism is no more than speculation, as in the case of aluminum in vaccines. But research published in just the past couple of years has now provided direct evidence that some of the other factors listed above could indeed increase the risk of autism.
For example, we know that autoimmune disease in mothers is a major risk factor. Specifically, a mother’s history of autoimmune thyroid disease, diabetes, psoriasis, or rheumatoid arthritis is associated with a 50 percent higher risk of autism.[xxii] The same conditions also appear to increase the risk of ADHD.[xxiii]
The rates of all of these autoimmune diseases have skyrocketed since the 1980s, which may account for some of the increase in developmental disorders. (In my second book, The Keystone Approach, I explain some of the causes for autoimmunity, such as vitamin D deficiency and a decline in the number of beneficial gut microbes.)
The connection between a mother’s autoimmunity and autism also hints at a bigger force at play: inflammation. The term “inflammation” refers to a system of defense mechanisms normally triggered by infections, damaged cells, or chemical irritants. The immune system switches to damage-control mode to remove the problem and initiate healing. Yet collateral damage can sometimes occur, particularly if inflammation continues unchecked for too long. For an infant, this collateral damage could include harm to their developing brain.
Autoimmunity is, however, only one possible cause of inflammation. Another cause is infection. There is now clear evidence that serious infections during critical developmental stages can increase the risk of autism, ADHD, and other mental disorders.[xxiv]
This link between infections and autism supports the overall paradigm that inflammation harms the developing brain, but it cannot explain the rise in the number of cases. That is because infectious diseases have existed throughout human history and their prevalence has been falling as autism has been rising.
Likewise, the recent rise in autoimmune disease only accounts for a small fraction of the autism and ADHD cases seen today. There is something much more pervasive at play, with a more widespread reach. Many experts now believe that the culprit may be exposure to environmental toxins.
Cynthia Nevison is one researcher who has been analyzing the rise in autism cases in the United States and comparing that to our level of exposure to environmental toxins over the same time period. Dr. Nevison notes that most of the suspected environmental toxins she looked at have actually decreased over the time period of interest, including lead, certain pesticides, and air pollution from vehicles. In many ways, our world is actually getting cleaner and less toxic.
But Dr. Nevison also reports there are some toxins that have increased in parallel with the rise in autism, notably: flame retardants, aluminum in vaccines, and the pesticide glyphosate, which is now heavily sprayed on wheat, corn, soy, and oats.[xxv] Acetaminophen also became the pain and fever reliever of choice during the 1980s–1990s, when autism began to skyrocket.
The fact that young children have been exposed to greater levels of these chemicals over the same time frame that autism has increased is obviously not sufficient to establish that any one of these toxins causes autism. However, for several toxins, such as pesticides, we actually do have direct evidence that exposure to high levels during pregnancy is a risk factor for autism, as will be discussed in the chapters that follow.
For other chemicals, where the evidence is more ambiguous, it may be the case that exposure only contributes to autism in particularly vulnerable children. This vulnerability may be because of genetics or because the children already have higher levels of inflammation due to nutrient deficiencies, the mother’s autoimmunity, infections, or exposure to other chemicals.
When we zoom out and look at the bigger picture, it appears that it is probably the combination of many different factors that contributes to autism risk. Any one factor alone may not be sufficient to cause autism, but when combined with other assaults that also trigger inflammation, it may be too much for a vulnerable brain to handle.
That is why we can have such a powerful influence with relatively simple steps. By minimizing exposure to certain toxins, we can reduce the risk posed by other factors that also cause inflammation. By ensuring adequate nutrient intake, we reduce the potential harms of toxins even further. In short, by changing the risk factors that are relatively easy to address, our children will be less vulnerable to other factors that are out of our hands. That leads to one overarching philosophy to keep in mind as you learn about all the various ways to protect your baby’s brain development: you can pick and choose what to focus on. You do not have to do everything discussed in this book to make a big impact. Even a few small changes will go a long way toward providing a safe and protective environment for your baby’s brain to grow. These changes can be as simple as taking the right supplements during pregnancy, as the next chapters explain. (For a broad overview of supplement recommendations, a summary list is provided at the end of chapter 6 of Brain Health from Birth.)
[i] Treffert, D. A. (1970). Epidemiology of infantile autism. Archives of General Psychiatry, 22(5), 431–438.
Lotter, V. (1966). Epidemiology of autistic conditions in young children. Social Psychiatry, 1(3), 124–135.
[ii] Xu, G., Strathearn, L., Liu, B., & Bao, W. (2018). Prevalence of autism spectrum disorder among US children and adolescents, 2014-2016. Jama, 319(1), 81–82.
[iii] Xu, G., Strathearn, L., Liu, B., & Bao, W. (2018). Prevalence of autism spectrum disorder among US children and adolescents, 2014-2016. Jama, 319(1), 81–82.
[iv] Boyle, C. A., Boulet, S., Schieve, L. A., Cohen, R. A., Blumberg, S. J., Yeargin-Allsopp, M., … & Kogan, M. D. (2011). Trends in the prevalence of developmental disabilities in US children, 1997–2008. Pediatrics, peds-2010.
[v] Danielson, M. L., Bitsko, R. H., Ghandour, R. M., Holbrook, J. R., Kogan, M. D., & Blumberg, S. J. (2018). Prevalence of parent-reported ADHD diagnosis and associated treatment among US children and adolescents, 2016. Journal of Clinical Child & Adolescent Psychology, 47(2), 199–212.
[vii] Silberman, S. (2015). Neurotribes: The Legacy of Autism and the Future of Neurodiversity. Penguin.
[viii] Handley, J. B. (2018). How to End the Autism Epidemic. Chelsea Green Publishing.
[ix] American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (DSM-5®). American Psychiatric Pub.
[x] Olmsted, D, Blaxill, M. Denial: How Refusing to Face the Facts about Our Autism Epidemic Hurts Children, Families, and Our Future. Skyhorse Publishing, 2017.
[xi] Buescher, A. V., Cidav, Z., Knapp, M., & Mandell, D. S. (2014). Costs of autism spectrum disorders in the United Kingdom and the United States. JAMA Pediatrics, 168(8), 721–728.
[xii] Mazurek, M. O., Kanne, S. M., & Wodka, E. L. (2013). Physical aggression in children and adolescents with autism spectrum disorders. Research in Autism Spectrum Disorders, 7(3), 455–465.
[xiii] Hallmayer, J., Cleveland, S., Torres, A., Phillips, J., Cohen, B., Torigoe, T., … & Lotspeich, L. (2011). Genetic heritability and shared environmental factors among twin pairs with autism. Archives of General Psychiatry, 68(11), 1095–1102.
Bourgeron, T. (2016). Current knowledge on the genetics of autism and propositions for future research. Comptes rendus biologies, 339(7-8), 300–307.
[xiv] Nevison, C. D. (2014). A comparison of temporal trends in United States autism prevalence to trends in suspected environmental factors. Environmental Health, 13(1), 73.
Parker, W., Hornik, C. D., Bilbo, S., Holzknecht, Z. E., Gentry, L., Rao, R., … & Nevison, C. D. (2017). The role of oxidative stress, inflammation and acetaminophen exposure from birth to early childhood in the induction of autism. Journal of International Medical Research, 45(2), 407–438
[xv] Handley, J. B. (2018). How to End the Autism Epidemic. Chelsea Green Publishing.
[xvi] Xu, G., Strathearn, L., Liu, B., & Bao, W. (2018). Prevalence of autism spectrum disorder among US children and adolescents, 2014-2016. Jama, 319(1), 81–82.
[xvii] Parker, W., Hornik, C. D., Bilbo, S., Holzknecht, Z. E., Gentry, L., Rao, R., … & Nevison, C. D. (2017). The role of oxidative stress, inflammation and acetaminophen exposure from birth to early childhood in the induction of autism. Journal of International Medical Research, 45(2), 407–438.
Copyright © 2017 by William Parker.
Reprinted by Permission of SAGE Publications, Ltd.
Data compiled by Nevison, C. D. (2014). A comparison of temporal trends in United States autism prevalence to trends in suspected environmental factors. Environmental Health, 13(1), 73.
[xviii] Treffert, D. A. (1970). Epidemiology of infantile autism. Archives of General Psychiatry, 22(5), 431–438.
Burd, L., Fisher, W., & Kerbeshian, J. (1987). A prevalence study of pervasive developmental disorders in North Dakota. Journal of the American Academy of Child & Adolescent Psychiatry, 26(5), 700–703.
Wing, L., Yeates, S. R., Brierley, L. M., & Gould, J. (1976). The prevalence of early childhood autism: comparison of administrative and epidemiological studies. Psychological Medicine, 6(1), 89–100.
[xix] Nevison, C. D. (2014). A comparison of temporal trends in United States autism prevalence to trends in suspected environmental factors. Environmental Health, 13(1), 73.
[xx] Saylor, K. E., & Amann, B. H. (2016). Impulsive aggression as a comorbidity of attention-deficit/hyperactivity disorder in children and adolescents. Journal of Child and Adolescent Psychopharmacology, 26(1), 19–25.
[xxi] Saylor, K. E., & Amann, B. H. (2016). Impulsive aggression as a comorbidity of attention-deficit/hyperactivity disorder in children and adolescents. Journal of Child and Adolescent Psychopharmacology, 26(1), 19–25.
[xxii] Wu, S., Ding, Y., Wu, F., Li, R., Xie, G., Hou, J., & Mao, P. (2015). Family history of autoimmune diseases is associated with an increased risk of autism in children: A systematic review and meta-analysis. Neuroscience & Biobehavioral Reviews, 55, 322–332.
Chen, S. W., Zhong, X. S., Jiang, L. N., Zheng, X. Y., Xiong, Y. Q., Ma, S. J., … & Chen, Q. (2016). Maternal autoimmune diseases and the risk of autism spectrum disorders in offspring: a systematic review and meta-analysis. Behavioural Brain Research, 296, 61–69
Croen, L. A., Qian, Y., Ashwood, P., Daniels, J. L., Fallin, D., Schendel, D., … & Zerbo, O. (2018). Family history of immune conditions and autism spectrum and developmental disorders: Findings from the study to explore early development. Autism Research.
[xxiii] Instanes, J. T., Halmøy, A., Engeland, A., Haavik, J., Furu, K., & Klungsøyr, K. (2017). Attention-deficit/hyperactivity disorder in offspring of mothers with inflammatory and immune system diseases. Biological Psychiatry, 81(5), 452–459.
[xxiv] Köhler-Forsberg, O., Petersen, L., Gasse, C., Mortensen, P. B., Dalsgaard, S., Yolken, R. H., … & Benros, M. E. (2019). A nationwide study in Denmark of the association between treated infections and the subsequent risk of treated mental disorders in children and adolescents. JAMA Psychiatry, 76(3), 271–279.
[xxv] Nevison, C. D. (2014). A comparison of temporal trends in United States autism prevalence to trends in suspected environmental factors. Environmental Health, 13(1), 73.