 Post-traumatic stress disorder, or PTSD, is a common condition that affects around 3% of people at any given time. At its core, PTSD is defined by a specific set of signs, symptoms, and behaviors that arise as following exposure to a life-threatening event. These include re-experiencing the trauma frequently through flashbacks and nightmares, constantly scanning the environment for threats, even when in safe situations, attempting to avoid people, places, or things that are reminiscent of the trauma, and cutting oneself off from their own emotions. Together, these symptoms and behaviors have the potential to turn a single traumatic event into years or even decades of fear and suffering. Traumatic experiences are common, with the majority of people around 60% experiencing at least one major trauma in their lifetime. However, only around 10% of people will go on to develop PTSD. This means that, while some people experience PTSD after a trauma, most do not. This can be a difficult thing to wrap your head around, especially in the medical field, where the most common way of looking at illness often involves a simple cause-and-effect explanation. We assume, for example, that everyone who catches a virus will become sick as a result. However, this model doesn't work with PTSD, as not everyone who experiences trauma will get this disorder. Why is this the case? When looking at who gets PTSD, two key factors become relevant, the trauma itself and the person experiencing it. Let's first take a look at the effect of the trauma itself. While all traumatic events must be life-threatening to the extent that they evoke intense feelings of fear, helplessness, and terror, this definition still encompasses a wide variation of experiences. Trauma can range from exposure to things like war, combat, and terrorism, to automobile accidents, animal attacks, and natural disasters. It is this variation that, at least in part, accounts for different rates of developing PTSD. For example, less than 10% of people who experience a non-intentional trauma, such as a workplace accident, will develop PTSD, while nearly 50% of those experiencing intentional trauma, such as assault, will. Whether the traumatic event occurred once, like a car crash, or repeatedly, like chronic abuse, matters as well. Other factors can also predict an increased risk of developing PTSD, in particular, people who are younger at the time of trauma, who went through their trauma alone, who had little or no time to process the experience, and who had low social support after the trauma, tended to be at the highest risk. The combined effect of these factors was vividly illustrated in veterans returning from the Vietnam War. Compared to those who served in World War II, Vietnam War soldiers were younger, 19 years on average, compared to 26, and were often assigned a tour of duty in predetermined timeframes, which broke up social cohesion, as opposed to soldiers in World War II who trained, fought, and returned home largely with the same group of peers. After the war, Vietnam War veterans had little time to process, as getting home by plane took less than a day, compared to the 30-day journey by ship that World War II vets experienced. Finally, upon returning home, Vietnam veterans received little social support, and many were greeted with protestors rather than parades. All of these factors together account for the fact that soldiers who fought in the Vietnam War developed PTSD at significantly higher rates than those returning from World War II, even though the nature of the trauma itself, military combat, was largely the same. However, these factors still don't tell the whole story. Otherwise, everyone who experienced the same trauma under the same circumstances would develop PTSD at roughly the same rate. In reality, studies on groups of veterans who fought together through the same traumatic events have shown that only about 20% develop PTSD, while the other 80% do not. To account for this, we need to look at factors specific to the person experiencing the trauma, and in particular, differences in how each person's brain processes dramatic events. Three regions of the brain in particular are involved here, the amygdala, the hippocampus, and the medial prefrontal cortex. These regions are all involved in regulating someone's fear response. When experiencing a life-threatening situation, the amygdala generates the initial surge of fear. The medial prefrontal cortex and the hippocampus then act to fine-tune the amygdala's response by integrating information about the environment as well as one's past experiences. Let's use an example to better understand how these three brain regions work together. Let's say that we suddenly hear the sound of a loud explosion. The amygdala immediately kicks in and interprets explosion as a dangerous thing, like a bomb. The amygdala then activates the sympathetic nervous system and its fight-or-flight response, inducing a state of fear. However, we then realize that the sound of the explosion is happening during a firework show on the 4th of July, and our fear response goes away. This is the role that the medial prefrontal cortex plays. It is able to take other sensory information, such as visuals of American flags and the emotional context of smiling faces around us, and integrate them into an unconscious thought that may be the explosion is nothing to be worried about after all. The medial prefrontal cortex then steps in to tell the amygdala to back off and allow us to enjoy the fireworks without being in an uncomfortable state of fear. The second brain region that acts as a break in the amygdala, the hippocampus, also helps to regulate the fear response, but this time by using memories of the past. Someone who sees another person in a scary mask may initially feel a sense of fear. However, they also know based on their experiences of holidays over their lifetime, that unsettling masks are nothing to be afraid of on Halloween, and this information is accessed via the hippocampus. So when this person goes out trick-or-treating, their hippocampus kicks into gear and suggests to the amygdala that things aren't as frightening as they seem. In contrast, for someone at high risk of developing PTSD, the amygdala is not only overactive, generating stronger-than-average fear responses, but the medial prefrontal cortex and hippocampus are both underactive, handicapping their ability to attenuate the fear response by using environmental cues and past memories. It is this combination of an overactive amygdala, an underactive medial prefrontal cortex, and an underdeveloped hippocampus that is most characteristic of PTSD. As someone with these traits is more likely to react to trauma with strong negative emotions and less able to integrate sensory information from the environment and memories of happier times in their lives to lessen the sting of a traumatic event. Understanding the contributions of both the trauma itself as well as the neurobiological traits of the person experiencing it allows us to unravel the enigma of trauma and work to ensure that the suffering caused by a traumatic event is kept to a minimum. It also helps to remove the stigma of PTSD by allowing people to recognize that in many cases the effects of trauma are largely out of our control. After all, the only thing worse than experiencing PTSD is to also believe that you are somehow weaker, sicker, or not trying as hard as the people around you. Trauma doesn't have to be the terrible gift that keeps on giving. By learning more about the nature of PTSD, we can get better at recognizing it in ourselves and others and find faster ways of getting help. Hi everyone, thanks for watching this latest video. If you're interested in this topic or in learning about mental health in general, consider checking out my new book, Memorable Psychiatry, which was just released a few months ago. If you're wanting to learn more about psychiatric medications, look at some of the other videos on my channel or my book, Memorable Psychopharmacology. Both books are available on Amazon. I'll put the link in the description below. In the meantime, if anyone has any questions or ideas for future videos, let me know in the comments. Thanks for watching. Bye for now.