Once a week.
Subscribe to our weekly newsletter.
The Bad News: Trauma Can Be Inherited. The Good News — So Can Resilience
This discovery could lead to a whole new class of drugs for psychiatric disorders.
We tend to understand where our physical traits come from. We may have our mother’s eyes or our father’s chin. But when it comes to personality traits, we tend to think of them as our own. Psychologists go one step farther. They see things like anxiety or depression stemming from personal experiences which shaped us. Some studies however reach back even farther, are in fact passed down from parents or even grandparents.
Neurosis, anxiety, an adventuresome spirit, can these be inherited? That was the question on the minds of two researchers back in 1992. Then molecular biologist and geneticist Moshe Szyf and neurobiologist Michael Meaney, both of Montreal’s McGill University, met after a conference and had a few beers in a nearby bar. They started discussing inheritable traits, and Meaney theorized that certain emotional traits could be passed down through genes inside the brain. Szyf though skeptical was intrigued.
DNA inhabits the nuclei of cells. Since the 1970’s, scientists had wondered what tells each cell to transcribe certain genes and discard others. It was found that molecules in the methyl group earmarked certain genes, tagging them for transcription. Because of the discovery of these methyl groups and their position, each sitting beside a corresponding gene, the field of epigenetics was born. The Greek prefix epi meaning over from. At first, it was thought that epigenetic changes only occurred in the fetal stage of life. Over time, scientists discovered that changes in diet, exposure to certain elements in the environment, and other encounters also changed our DNA.
Artist’s rendition of DNA methylation. By Christoph Bock (Max Planck Institute for Informatics) - Own work, CC BY-SA 3.0
What Prof. Meaney hypothesized was that a parent who experienced a trauma could have certain changes in their brain which might lead to epigenetic changes that were passed on, inhabiting the neurons of their children’s brains or even their grandchildren. That rumination bore an entirely new field, behavioral epigenetics. That means if you had a parent or grandparent who lived through a genocide, war, saw someone murdered, or who suffered a different trauma, say at the hands of an abusive or neglectful parent, you carry traits for the emotional impact in your genes.
A grandfather who was neglected as a child for instance, may have experienced depression, and so passed that predisposition onward. It works in the positive sense too. If your grandfather had loving, nurturing parents, you get a genetic boost in the psychological and behavioral sense. How far does this epigenetic influence go? It’s pretty hard to parse out, even for scientists.
Meaney was able to prove that certain emotional traits were passed down by studying female rats and their pups. He and colleagues gathered data reaching back to the 1950’s. Those baby rats handled by researchers, for as little as five minutes a day, during the first few weeks after birth, were calmer and less stressed than those who were never handled. Meaney and colleagues found this was not due to human handling.
Instead, mother rats were more likely to groom their pups after humans had touched them. They also tended to give them more room for suckling. This extra attention led to better adjusted pups. Meaney showed that the more attention an infant rat received, the lower their stress hormone level in adulthood was. He said, "What we had done up to that point in time was to identify maternal care and its influence on specific genes.” It was after this experiment that Meaney met Szyf.
Syrian refugees. Those who endure dramatic experiences pass epigenetic changes down to their offspring.
The pair conducted an array of experiments. They began by selecting highly attentive mother rats and those who were neglectful. The offspring of neglectful mothers were more anxious and easily startled. Researchers took the offspring of these rats in adulthood and examined their brains, specifically the hippocampus. This is the area that has to do with stress, anxiety, and the formation of memories.
Those who had neglectful mothers had observable changes in the methylation of the genes there. These changes produced more glucocorticoid receptors, which interact with the stress hormone. More of them means a higher sensitivity to stress. Those with diligent mothers did not display such changes.
Next, Meaney and Szyf took a group of pups raised by neglectful mothers. They injected their brains with a drug called trichostatin A. This removes methyl groups. None of the skittishness seen in their mothers was found in this group. Their brains were once again examined, and no epigenetic changes were found. “It was like rebooting a computer,” Szyf said.
In a 2008 study, the pair found that neglectful mother rats had fewer estrogen receptors in their brain. When their female offspring matured, this resulted in fewer estrogen receptors in their brains, which led to neglect of their own young. Meaney and Szyf had discovered what is now called postnatal inheritance, or epigenetic changes from the environment that are written into our DNA, and then passed down to the next generation. These two scientists have published 24 papers on the subject since.
Next, the researchers moved on to human subjects. In a 2008 study, Meaney and Szyf examined the brains of those who committed suicide, and compared them with those who had died for other reasons. Among the suicidal, neural genes in the hippocampus showed excessive methylation. Since their brains were so methylated, researchers concluded that suicidal subjects must have been abused as children. This could be why someone who had neglectful or abusive parents must struggle to overcome the trauma they endured. Methyl groups in their neural genes bind them to feelings of anxiety, hopelessness, malaise, or worry. Of course, due to ethical concerns, examining the brains of living humans is out of the question. Professor Szyf however has located signs of epigenetic methylation in blood samples.
An orphans suffering may affect their genome, long-term.
In one experiment, Szy and researchers from Yale recruited 14 Russian children brought up in an orphanage, and 14 others raised by their parents. Each gave a blood sample which was examined. Orphans had far more methylation than those who were raised by their parents. Areas of the brain important for communication and brain development were most affected.
The study concluded that separation from biological parents causes early stress that effects the person’s genome, long-term. This in turn could explain why adopted children may be more susceptible to damage from harsh parenting styles, on the part of adoptive parents. Study co-author, psychologist Elena Grigorenko wrote, “Parenting adopted children might require much more nurturing care to reverse these changes in genome regulation.”
The most exciting revelation was from a study last year out of New York’s Mount Sinai hospital. 32 holocaust survivors and their children had their genes analyzed. A methylation tag was found in a stress-related gene in parents and children alike. “The gene changes in the children could only be attributed to Holocaust exposure in the parents,” said Rachel Yehuda, lead researchers on the study.
More research must be done to understand the processes involved. How epigenetic changes are passed on from parent to offspring still remains Unknown. Though we may despair that our parents or grandparents trauma lives on in us, Prof. Yehuda says other, related methylation tags may make us more resilient, which could be passed down too.
Some researchers take it a step further. It could be that many or even most of our emotional and psychological tendencies, whether we are intellectual or tactile, communicative or quiet, emotional or stoic, forgetful or possess a perfect memory, might all arise from epigenetic changes passed down from our ancestors. What’s more, this breakthrough could lead to big changes in how we treat psychiatric conditions. Big Pharma and small biotech startups alike are already hunting for compounds, hoping to launch the next generation of drugs for psychiatric disorders, ones that are more effective, with very few, if any, side effects.
To learn more about the holocaust study and it’s implication for mental health click here:
Evolution doesn't clean up after itself very well.
- An evolutionary biologist got people swapping ideas about our lingering vestigia.
- Basically, this is the stuff that served some evolutionary purpose at some point, but now is kind of, well, extra.
- Here are the six traits that inaugurated the fun.
The plica semilunaris<img class="rm-lazyloadable-image rm-shortcode" type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTA5NjgwMS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY3NDg5NTg1NX0.kdBYMvaEzvCiJjcLEPgnjII_KVtT9RMEwJFuXB68D8Q/img.png?width=980" id="59914" width="429" height="350" data-rm-shortcode-id="b11e4be64c5e1f58bf4417d8548bedc7" data-rm-shortcode-name="rebelmouse-image" />
The human eye in alarming detail. Image source: Henry Gray / Wikimedia commons<p>At the inner corner of our eyes, closest to the nasal ridge, is that little pink thing, which is probably what most of us call it, called the caruncula. Next to it is the plica semilunairs, and it's what's left of a third eyelid that used to — ready for this? — blink horizontally. It's supposed to have offered protection for our eyes, and some birds, reptiles, and fish have such a thing.</p>
Palmaris longus<img class="rm-lazyloadable-image rm-shortcode" type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTA5NjgwNy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzMzQ1NjUwMn0.dVor41tO_NeLkGY9Tx46SwqhSVaA8HZQmQAp532xLxA/img.jpg?width=980" id="879be" width="1920" height="2560" data-rm-shortcode-id="4089a32ea9fbb1a0281db14332583ccd" data-rm-shortcode-name="rebelmouse-image" />
Palmaris longus muscle. Image source: Wikimedia commons<p> We don't have much need these days, at least most of us, to navigate from tree branch to tree branch. Still, about 86 percent of us still have the wrist muscle that used to help us do it. To see if you have it, place the back of you hand on a flat surface and touch your thumb to your pinkie. If you have a muscle that becomes visible in your wrist, that's the palmaris longus. If you don't, consider yourself more evolved (just joking).</p>
Darwin's tubercle<img class="rm-lazyloadable-image rm-shortcode" type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTA5NjgxMi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0ODUyNjA1MX0.8RuU-OSRf92wQpaPPJtvFreOVvicEwn39_jnbegiUOk/img.jpg?width=980" id="687a0" width="819" height="1072" data-rm-shortcode-id="ff5edf0a698e0681d11efde1d7872958" data-rm-shortcode-name="rebelmouse-image" />
Darwin's tubercle. Image source: Wikimedia commons<p> Yes, maybe the shell of you ear does feel like a dried apricot. Maybe not. But there's a ridge in that swirly structure that's a muscle which allowed us, at one point, to move our ears in the direction of interesting sounds. These days, we just turn our heads, but there it is.</p>
Goosebumps<img class="rm-lazyloadable-image rm-shortcode" type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTA5NzMxNC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyNzEyNTc2Nn0.aVMa5fsKgiabW5vkr7BOvm2pmNKbLJF_50bwvd4aRo4/img.jpg?width=980" id="d8420" width="1440" height="960" data-rm-shortcode-id="8827e55511c8c3aed8c36d21b6541dbd" data-rm-shortcode-name="rebelmouse-image" />
Goosebumps. Photo credit: Tyler Olson via Shutterstock<p>It's not entirely clear what purpose made goosebumps worth retaining evolutionarily, but there are two circumstances in which they appear: fear and cold. For fear, they may have been a way of making body hair stand up so we'd appear larger to predators, much the way a cat's tail puffs up — numerous creatures exaggerate their size when threatened. In the cold, they may have trapped additional heat for warmth.</p>
Tailbone<img class="rm-lazyloadable-image rm-shortcode" type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTA5NzMxNi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY3MzQwMjc3N30.nBGAfc_O9sgyK_lOUo_MHzP1vK-9kJpohLlj9ax1P8s/img.jpg?width=980" id="9a2f6" width="1440" height="1440" data-rm-shortcode-id="4fe28368d2ed6a91a4c928d4254cc02a" data-rm-shortcode-name="rebelmouse-image" />
Image source: Decade3d-anatomy online via Shutterstock<p>Way back, we had tails that probably helped us balance upright, and was useful moving through trees. We still have the stump of one when we're embryos, from 4–6 weeks, and then the body mostly dissolves it during Weeks 6–8. What's left is the coccyx.</p>
The palmar grasp reflex<img class="rm-lazyloadable-image rm-shortcode" type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTA5NzMyMC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzNjY0MDY5NX0.OSwReKLmNZkbAS12-AvRaxgCM7zyukjQUaG4vmhxTtM/img.jpg?width=980" id="8804c" width="1440" height="960" data-rm-shortcode-id="67542ee1c5a85807b0a7e63399e44575" data-rm-shortcode-name="rebelmouse-image" />
Palmar reflex activated! Photo credit: Raul Luna on Flickr<p> You've probably seen how non-human primate babies grab onto their parents' hands to be carried around. We used to do this, too. So still, if you touch your finger to a baby's palm, or if you touch the sole of their foot, the palmar grasp reflex will cause the hand or foot to try and close around your finger.</p>
Other people's suggestions<p>Amir's followers dove right in, offering both cool and questionable additions to her list. </p>
Fangs?<blockquote class="twitter-tweet" data-conversation="none" data-lang="en"><p lang="en" dir="ltr">Lower mouth plate behind your teeth. Some have protruding bone under the skin which is a throw back to large fangs. Almost like an upsidedown Sabre Tooth.</p>— neil crud (@neilcrud66) <a href="https://twitter.com/neilcrud66/status/1085606005000601600?ref_src=twsrc%5Etfw">January 16, 2019</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
Hiccups<blockquote class="twitter-tweet" data-conversation="none" data-lang="en"><p lang="en" dir="ltr">Sure: <a href="https://t.co/DjMZB1XidG">https://t.co/DjMZB1XidG</a></p>— Stephen Roughley (@SteBobRoughley) <a href="https://twitter.com/SteBobRoughley/status/1085529239556968448?ref_src=twsrc%5Etfw">January 16, 2019</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
Hypnic jerk as you fall asleep<blockquote class="twitter-tweet" data-conversation="none" data-lang="en"><p lang="en" dir="ltr">What about when you “jump” just as you’re drifting off to sleep, I heard that was a reflex to prevent falling from heights.</p>— Bann face (@thebanns) <a href="https://twitter.com/thebanns/status/1085554171879788545?ref_src=twsrc%5Etfw">January 16, 2019</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script> <p> This thing, often called the "alpha jerk" as you drop into alpha sleep, is properly called the hypnic jerk,. It may actually be a carryover from our arboreal days. The <a href="https://www.livescience.com/39225-why-people-twitch-falling-asleep.html" target="_blank" data-vivaldi-spatnav-clickable="1">hypothesis</a> is that you suddenly jerk awake to avoid falling out of your tree.</p>
Nails screeching on a blackboard response?<blockquote class="twitter-tweet" data-conversation="none" data-lang="en"><p lang="en" dir="ltr">Everyone hate the sound of fingernails on a blackboard. It's _speculated_ that this is a vestigial wiring in our head, because the sound is similar to the shrill warning call of a chimp. <a href="https://t.co/ReyZBy6XNN">https://t.co/ReyZBy6XNN</a></p>— Pet Rock (@eclogiter) <a href="https://twitter.com/eclogiter/status/1085587006258888706?ref_src=twsrc%5Etfw">January 16, 2019</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
Ear hair<blockquote class="twitter-tweet" data-conversation="none" data-lang="en"><p lang="en" dir="ltr">Ok what is Hair in the ears for? I think cuz as we get older it filters out the BS.</p>— Sarah21 (@mimix3) <a href="https://twitter.com/mimix3/status/1085684393593561088?ref_src=twsrc%5Etfw">January 16, 2019</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
Nervous laughter<blockquote class="twitter-tweet" data-lang="en"><p lang="en" dir="ltr">You may be onto something. Tooth-bearing with the jaw clenched is generally recognized as a signal of submission or non-threatening in primates. Involuntary smiling or laughing in tense situations might have signaled that you weren’t a threat.</p>— Jager Tusk (@JagerTusk) <a href="https://twitter.com/JagerTusk/status/1085316201104912384?ref_src=twsrc%5Etfw">January 15, 2019</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
Um, yipes.<blockquote class="twitter-tweet" data-conversation="none" data-lang="en"><p lang="en" dir="ltr">Sometimes it feels like my big toe should be on the side of my foot, was that ever a thing?</p>— B033? K@($ (@whimbrel17) <a href="https://twitter.com/whimbrel17/status/1085559016011563009?ref_src=twsrc%5Etfw">January 16, 2019</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
Are we enslaved by the finer things in life?
- The Roman writer, Tacitus, argued that the Roman Empire was built by enslaving conquered people who became accustomed to fine living and luxury.
- Technology today has become so essential to our daily lives that it seems impossible to break free of it. It's as much a cage as a luxury.
- Being dependent on a thing gives it power over you. To need something or someone is, for better or worse, to limit yourself.
- There was a massive die-off of marine life 359 million years ago, and nobody knows why.
- A new study proposes that the Late Devonian extinction may have been caused by one or more nearby supernovae.
- The supernova hypothesis could be confirmed if scientists can find "the green bananas of the isotope world" in the geologic record.
Fifty years of research on children's toy preferences shows that kids generally prefer toys oriented toward their own gender.