For all the research that has been done on the human brain over the last few decades, we still know very little about how a lot of conditions happen.

A number of mental illnesses have come to light, including clinical depression, bipolar disorder, borderline personality disorder, and of course, post-traumatic stress disorder (or PTSD). These are conditions experienced by literally millions of people worldwide, but we still have a lot to learn about how these conditions develop within the people who suffer from them.

PTSD is one that has taken literal decades for us to understand even as well as we do know. First recorded as "shell-shock" during the First World War, it was primarily recognized in soldiers returning home from the frontlines, whose experiences when facing death on a mass-scale had changed them mentally.

However, as the condition was revealed to have much more to do with personal trauma, we've come to find out that plenty of non-combat traumatic situations can cause forms of PTSD as well. Most significantly, researchers have made something of a huge breakthrough; you may actually be able to inherit PTSD from your ancestors.

One group of people in particular may be really susceptible to this...

As we move further and further away from the years of World War II, survivors of the Holocaust, one of the single most traumatic and horrific events in human history, have ever-expanding families that they continue to share their experiences with. Well it turns out, they might actually be sharing something else as well.

Survivors have been found to have lower levels of cortisol, the chemical in your brain that allows it to recover from trauma. While this part isn't surprising in the slightest, what IS surprising is the fact that researchers at the Icahn School of Medicine at Mount Sinai and the James J. Peters Veterans Affairs Medical Center in Bronx, N.Y. have discovered that this lower level of cortisol appears to be passed down to their descendants.

While there isn't any conclusive proof yet, the research done by these teams has some pretty massive implications if it turns out to be correct. It would mean that PTSD can be passed down genetically, and that doctors may have to keep a closer eye on the children of PTSD sufferers to keep them from developing their own slew of mental issues.

What do you think about the possibility of PTSD being passed down genetically?