Epigenetics

Environmental factors can predetermine your adult physical and mental health.

Posted Jun 04, 2018

Pixabay
Source: Pixabay

We have long been told that our genes rule and there’s nothing much we can do about it.  Even the latest research holds that our genes account for childhood anxiety, which in turn is the gateway to all future mental issues.

But now, an article in The New York Review of Books notes environmental factors that arise in early childhood can predetermine our future mental and physical health, including heart disease, cancer, mood and dietary disorders, alcohol and drug abuse, infertility, suicidal behavior, hyperactivity, learning deficits, and sleep disorders.

The basis for heritable environmental factors is that excessive stress or deprivation, whether experienced in early childhood or while in utero, affects our genetic programming by making long-lasting changes in the way our genes are expressed. By blocking access to certain genes, this mechanism can program us to experience future feelings of depression, anxiety or paranoia. And most surprisingly, these changes can be passed on to future generations that have never directly experienced the stresses or deprivations.    

An example might be future obesity. The fetus, newborn, or child suffers continuing stress from hunger. But when food becomes available, the stress response cannot shut off, but continues as if the body thermostat is broken. Instead of feeling satiated when a certain amount of food is ingested, we keep craving more food. The long-term consequences can be inflammation, diabetes, heart-disease, major depressive disorder, and schizophrenia.

Formerly, it was widely accepted that Darwinian evolutionary mechanisms were responsible for such long-lasting changes in brain function, but now we have evidence that epigenetic mechanisms can make such changes in the lifetime of a single person. The problem is that these changes may make us perpetually prepared for stresses and deprivations that no longer exist in a normalized environment. 

The stresses and deprivations arising from natural disasters, famine, and the atrocities of war could contribute to a maladaptation on the part of this epigenetic mechanism, not just at the individual level, but among large groups, leading to psychological disease and ill health even upon return to a normalized environment. The most widely studied example was the Dutch Hunger Winter in 1944, when the Germans prevented food from entering. Children born during this period had an increase of obesity and schizophrenia as adults. Also, during the Great Chinese Famine (1958-1961), women who experienced famine gave birth to children with obesity, diabetes, hypertension and impaired cognitive function as adults, along with an uptick in schizophrenia.    

Interestingly, research from the Archives of General Psychiatry has shown that the risk of schizophrenia in offspring from maternal exposure to acute food deprivation arises in the first-trimester. The Nazi blockade in 1944 to 1945 created a unique if tragic natural experiment to test three regions of Holland. In the west, or famine region, birth cohorts exposed to severe food deprivation during the first trimester showed a substantial increase in hospitalized schizophrenia for adult women, but not for men. Moderate food deprivation during the first trimester was not associated with increased risk of schizophrenia in the famine region. In the north and south regions, numbers were smaller and there was no exposure to severe famine.

Consistent with these maladaptive changes, we might ask if our current malaise of depression, anxiety and paranoia, reported in the media to be at epidemic levels, could be the result of epigenetic mechanisms carried over from stresses and deprivations borne by our forebears. But since almost everyone’s forebears have suffered at one time or another from famine, economic deprivations, pestilence, plagues, and the atrocities of war, ths pursuit of an answer can be pointless.  

A more meaningful takeaway might suggest that that the fetus is prone to future physical and mental issues arising from exposure to unhealthful environmental stresses particularly during the first trimester.

This blog was co-published with PsychResilience.com

References

Rosenfield I and Ziff E. (2018) New York Review of Books, Epigenetics: The Evolution Revolution, v LXV, n 10

Susser ES & Lin SP (1992) Archives of General Psychiatry, Schizophrenia after prenatal exposure to the Dutch Hunger Winter of 1944-1945, Dec;49(12):983-8.