The memories of seventh grade have mostly receded from view for most of us.

How well can you recall the faces of your fellow students? Can you summon the names of the teachers, the secretary, and the principal? Can you hear the way the bell sounded? How about the smell of the cafeteria on sloppy-joe day? The ache of your first crush? The panic of finding yourself in the bathroom at the same time as the school bully?

Maybe it's all strikingly clear. Or maybe, over time, your middle-school years have been lost in the fog of so many other childhood memories.

For a long time now, we've understood that we shoulder our experiences in the knapsack of our psyche. Even things you cannot consciously recall are somewhere in there, swimming around in your subliminal mind, ready to emerge unexpectedly for good or ill.

But it's all much deeper than that, because your body is in a constant state of transformation and regeneration, and your experiences, no matter how seemingly inconsequential, from bullies to crushes to sloppy joes, have all left an indelible mark within you -- and more importantly, within your genome.

In a single generation, genetic traits can change and be changed forever, as shown through the exciting world of epigenetics. Our genes actually change as a result of life conditions.

Until very recently, we've been thinking and speaking about the serious and long-term ramifications of bullying in predominantly psychological terms. Everyone agrees that bullying can leave very significant mental scars. The immense psychic pain some children and teens experience can even lead them to consider and act on desires to physically harm themselves.

But what if our experiences of being bullied did a lot more than just saddle us with some serious psychological baggage? Well, to answer that question, a group of researchers from the UK and Canada decided to study sets of monozygotic "identical" twins from the age of 5. Besides having identical DNA, each twin pair in the study had never been bullied up until that point.

You'll be glad to know that these researchers were not allowed to traumatize their subjects, unlike how the Swiss mice were handled. Instead, they let other children do their scientific dirty work.

After patiently waiting for a few years, the scientists revisited only the twin pairs where one of the twins in the pair had been bullied. When they dropped back into the now-12-year-old twins' lives, they found that present now was a striking epigenetic difference that had not been there when the children were 5. The researchers found significant change only in the twin who had been bullied. This means, in no uncertain genetic terms, that bullying isn't just risky in terms of self-harming tendencies for youth and adolescents; it actually changes how our genes work and how they shape our lives, and likely what we pass along to future generations.

What does that change look like genetically? Well, on average, in the bullied twin a gene that codes for a protein that helps move the neurotransmitter serotonin into neurons called SERT had significantly more DNA methylation in its promoter region. This change is thought to dial down the amount of proteins that can be made from the SERT gene -- meaning the more it's methylated, the more it's "turned off."

The reason that these findings are significant is that these epigenetic changes are thought to be able to persist throughout our lives. This means that even if you can't remember the details of being bullied, your genes certainly do.

But that's not all that these researchers found. They also wanted to see if there were any psychological changes between the twins to go along with the genetic ones that they'd observed. To test that, they subjected the twins to certain types of situational testing, which included public speaking and mental arithmetic -- experiences that most of us find stressful and would rather avoid. They discovered that one of the twins, the one with a history of being bullied (with a corresponding epigenetic change), had a much lower cortisol response when exposed to those unpleasant situations. Bullying not only turned those children's SERT gene to "low" but turned down their levels of cortisol when stressed.

A spike of cortisol can help us through a tough situation. But having too much cortisol for too long can short-circuit our physiology pretty quickly. So having a blunted cortisol response to stress was the twin's epigenetic reaction to be being bullied. In other words, the twin's epigenome changed in response in order to protect them from too much sustained cortisol. This compromise is a beneficial epigenetic adaptation in these children that helps them survive persistent bullying. The implications of this are nothing short of staggering.

Many of our genetic responses to our lives work in such a fashion, favoring the short term over the long term. Sure, it's easier in the short term to dull our response to persistent stress, but in the long run, epigenetic changes that cause long-term blunted cortisol responses can cause serious psychiatric conditions such as depression and alcoholism. And not to scare you too much, but those epigenetic changes are likely heritable from one generation to the next.

In the meantime, given the tremendous amount we've learned about what inheritance really means and what we can do to impact our genetic legacy -- in ways both good (spinach, perhaps) and bad (stress, it would appear) -- you are far from helpless.

While it may not always be possible to break completely free from your genetic inheritance, the more you learn, the more you will come to understand that the choices you make can result in a big difference in this generation, the next one, and possibly everyone else down the line.

We've always known that our genes shape our lives. But we're learning now that our lives shape our genes. This gives us one more reason to make sure that the early lives of our children are free of bullying and other unnecessary or potentially damaging stressors. By doing so, we may be helping not only our children but our ancestors for generations to come.

Need help? In the U.S., visit stopbullying.gov.