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Epidemics of the 21st Century

Epigenetics may contribute to the rise in mental and physical illness.

Key points

  • The last century has seen profound changes in diet, chemical exposures and the social milieu that contribute to mental and physical illness.
  • Some of these changes alter epigenetics, which can change the way genes are expressed and will be passed from one generation to the next.
  • Epigenetic transmission means that both physical and emotional traumas are cumulative over generations.

I’ve been a doctor for over 40 years and I’ve witnessed many changes, including epidemic rises in multiple medical conditions. I’m not talking about the present pandemic, nor am I referring to the opioid crisis, another devastating epidemic that has taken the lives of over 500,000 Americans. I’m talking about chronic conditions that cause a slow burn and sometimes kill.

Lyme disease is one example. But think how things have changed since the beginning of the previous century: heart disease was barely on the radar in 1900, but for over 50 years, it has been the number one cause of death in the U.S.1 A whopping 69 percent of Americans are now overweight, with 36.5 percent obese,2 directly contributing to the skyrocketing incidence of adult-onset diabetes mellitus (AODM).3 When I was in training in the 1970s, I never saw a patient with AODM who was under 40 years old; now type 2 diabetes is being diagnosed in children.

And then there are the dramatic increases in autism spectrum disorder,4 attention deficit hyperactivity disorder (ADHD),5 autoimmune conditions,6 some types of cancer,7 and food allergies.8 Twenty-five years ago, when I had a large environmental medicine practice, most of my patients with food sensitivities reacted to one or more of a half-dozen foods: milk, corn, eggs, wheat, citrus, or sugar/yeast. It was easy to put patients on an elimination diet: fish, lamb, vegetables, legumes, potatoes, and rice. Now people react to avocados, rice, lettuce, and anything under the sun.

And, of course, there’s the rise in mental health disorders. Even before the Covid pandemic, the World Health Organization predicted that depression would become the leading cause of death globally.9 According to the CDC, in 2019, 19 percent of Americans suffered from depression in the U.S., and 7 percent were moderately to severely affected.10 Among adults, suicidal ideation is increasing; suicide has become the second leading cause of death in children and adolescents ages 13 to 19 — and the leading cause of death among 13 year-olds.11 (Among all Americans, it is the tenth leading cause of death.11)

Epigenetic Changes and Illness

There are a host of factors that determine how, where and why illness occurs. These include genetic proclivity, lifestyle, trauma, diet, exposures to microbes and toxins. But here is what may be further catapulting these seemingly disparate epidemics: a change in the human condition that we now understand as epigenetics.

While it takes millennia of natural selection to change our genes, specific proteins that turn genes on and off can alter gene expression in a single generation. Epigenetics explains how a change in the expression of genes can be passed from one generation to the next without actually changing the DNA. There are literally thousands of conditions that can cause epigenetic changes.

Nutrient deficiencies, exacerbated by soil depletion, can activate epigenetic changes that may result in neurological issues — from mood and behavioral disorders to cognitive dysfunction, and these problems may be passed on to subsequent generations.12,13 Epigenetics may help explain why the skyrocketing sugar intake in our diets is causing obesity.14,15

Chemical exposures may also have epigenetic consequences. Over the past century, we have been exposed to hundreds of thousands of chemicals that are new to human existence. Pesticides, insecticides, herbicides, and other chemicals all have the potential to modify epigenetic activity.16 Countless agents now ubiquitous in daily life, from air pollution to air fresheners and fabric softeners can negatively impact overall health.18,19

Changes in Our Social Lives

But it is not only diet, nutrition, and exposure to toxic chemicals that have changed in the past century. Another situation that has undergone a radical transformation is the social milieu. The social sphere, which used to revolve around communities, has devolved to extended families, then to nuclear families, then single-parent families, and now, tragically at times, to homeless families or just plain solitude.

It is no longer routine for people to go next door to be held by grandma, or move in with aunts and uncles when the going at home gets rough; in essence, safe shelter has disappeared. This lack of safety is compounded for survivors of childhood trauma, who can develop epigenetic abnormalities and may pass the trauma on to their offspring.20

That’s right—PTSD can be inherited. A review paper by Rachel Yehuda and Amy Lehrner on intergenerational transmission of trauma and the role of epigenetic mechanisms states, “There is now converging evidence supporting the idea that offspring are affected by parental trauma exposures occurring before their birth, and possibly even prior to their conception. On the simplest level, the concept of intergenerational trauma acknowledges that exposure to extremely adverse events impacts individuals to such a great extent that their offspring find themselves grappling with their parents’ post‐traumatic state.”21

PTSD is not only a psychological disorder, it can trigger increasing dysregulation of an individual’s neurobiology.22

Other social factors also have an enormous impact on health and well-being. Social isolation is a major risk factor for depression.23 The chronic stresses of poverty, racism, homophobia, and misogyny not only make for a bad day, but they can also act on our biochemical pathways impacting immune, hormonal, and neurological function.24 The long-term release of the stress hormone cortisol and of proteins called cytokines (which regulate the body’s immune system response) can cause even more damage. These biochemical messengers, in turn, may result in epigenetic changes that are passed on to future generations.25

Passing on Trauma

Epigenetic transmission means that both physical and emotional traumas are cumulative over generations. And these alterations in epigenetics are manifesting in a tsunami that may be destabilizing individuals’ core regulatory systems. In some cases, people respond as if they have continuous PTSD—their nervous and immune systems going haywire at both real and imagined threats, with all the downstream consequences.

This brings us back to pediatric acute-onset neuropsychiatric syndrome (PANS), which I have been discussing in the past few posts. I think we are witnessing an epidemic of autoimmune reactivity to multiple agents in the environment—such as foods, viruses, bacteria, and mold. We may be seeing it with SARS-CoV-2. When autoimmune reactivity results in neuroinflammation, it may result in cognitive dysfunction, PANS and a panoply of mental health disorders—for generations to come.

We need to become more cognizant of the cumulative stresses that result in combined mental and physical issues, and address them at their core.










9. Tucci V, Moukaddam N. We are the hollow men: The worldwide epidemic of mental illness, psychiatric and behavioral emergencies, and its impact on patients and providers. J Emerg Trauma Shock. 2017;10(1):4-6. doi:10.4103/0974-2700.199517



12. Liu J, Zhao SR, Reyes T. Neurological and Epigenetic Implications of Nutritional Deficiencies on Psychopathology: Conceptualization and Review of Evidence. Qi L, ed. Int J Mol Sci. 2015;16(8):18129-18148.



15. Ling C, Rönn T. Epigenetics in Human Obesity and Type 2 Diabetes. Cell Metab. 2019;29(5):1028-1044.

16. Collotta M1, Bertazzi PA, Bollati V. Epigenetics and pesticides. Toxicology. 2013 May 10;307:35-41.

17. Smith CM, Vera MKM, Bhandari RK. Developmental and epigenetic effects of Roundup and glyphosate exposure on Japanese medaka (Oryzias latipes). Aquat Toxicol. 2019 May;210:215-226. doi: 10.1016/j.aquatox.2019.03.005. Epub 2019 Mar 7. PMID: 30875550.



20. Matosin N, Cruceanu C, Binder EB. Preclinical and Clinical Evidence of DNA Methylation Changes in Response to Trauma and Chronic Stress. Chronic stress (Thousand Oaks). 2017;1:10.

21. Yehuda R, Lehrner A. Intergenerational transmission of trauma effects: putative role of epigenetic mechanisms. World Psychiatry. 2018;17(3):243-257.

22. McFarlane AC. The long-term costs of traumatic stress: intertwined physical and psychological consequences. World Psychiatry. 2010;9(1):3-10.

23. Bhatti AB, Haq A ul. The Pathophysiology of Perceived Social Isolation: Effects on Health and Mortality. Muacevic A, Adler JR, eds. Cureus. 2017;9(1):e994.

24. Song H et. al. Association of Stress-Related Disorders With Subsequent Autoimmune Disease. JAMA. 2018;319(23):2388-2400.

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