Neurobiology of PTSD

By Derek Martinez

Post Traumatic Stress Disorder, or PTSD for short, is one of the most common psychological disorders in the United States with up to 3 million cases per year. Many may be familiar with the psychological effects of PTSD from popular media that mainly involves veterans, who are at a higher risk for PTSD than most people. But there are just as many neurobiological factors that influence PTSD.

If you are not familiar with it, PTSD is a disorder that develops after witnessing or experiencing a major traumatic event. It is usually diagnosed when symptoms such as nightmares, flashbacks, and severe anxiety persist even months after the event has already occurred. Those with PTSD also suffer from anxiety/panic attacks due to “triggers,” which are external stimuli similar to those associated with the trauma. An example of this is if a person who has experienced a fire in their home smells smoke, he or she may start to feel that he or she is reliving the trauma again. These types of triggers are common for victims of natural disasters.

Let’s talk about why these triggers develop. The amygdala in the frontal lobe of our brain allows us to perceive stimuli from our sense organs and experience emotional reactions to them. These reactions also include fear. When the amygdala interprets fear, it sends a distress signal to the hypothalamus, triggering the “fight or flight” response, which releases cortisol and adrenaline in response to the perceived dangers. With PTSD, the brain learns to associate certain sense details with a traumatic event. When a person with PTSD perceives certain stimuli that their brain associated with the event, the amygdala sends the distress signal associated with fear even if there is no actual threat, meaning that the stimuli itself is considered a threat even before the brain fully processes a situation.

Location of the amygdala within other parts of the brain. Wikimedia Commons.

Because of this response, PTSD therapy often includes the skill of stimulating your brain with logical concepts and thoughts such as arithmetic to regulate the response to triggers. Since the amygdala is a central hub for emotional responses, doing something as simple as solving a math problem would counter the fight or flight response as it would stimulate the left side of your brain (associated with logical thought and reasoning) rather than the right side (associated with emotion and holistic perception). PTSD patients also practice intentionally reliving the event to condition themselves to the fear response and essentially “rewire” their brain to not cause such a stressful response to the stimuli.

Besides the amygdala's response, patients with PTSD are also affected by other abnormalities within the brain and other parts of the body. Two neurochemical features that are altered are catecholamines (hormones made by the adrenal glands, located on top of the kidneys) and the hippocampus (another part of the brain). With catecholamines, there is an increase of dopamine and norepinephrine levels/activity. The increase in dopamine interferes with fear conditioning (a paradigm developed for organisms to predict aversive events), while the increase in norepinephrine (a hormone which increases brain mobility and improves attention) increases arousal and startle response, and also an increase in pulse, blood pressure, and response to memories. The hippocampus has reduced volume and activity, which alters stress responses and the extinction of conditioned fear, which is learned by organisms as a survival mechanism. All of these factors play into the triggers of PTSD and long term/constant effects.

Though the path to treating psychological disorders like PTSD is long and difficult, learning the actual neurobiology behind disorders can be unexpectedly helpful and almost comforting to those with PTSD and other disorders. With this knowledge, patients are able to recognize their symptoms faster and receive more effective treatment.

Education Section

Q: What is the amygdala’s role in the brain?

A: The amygdala is the central hub for processing stimuli from sense organs and causing an emotional response to the stimuli. When the amygdala senses fear, it sends a distress signal to the hypothalamus, triggering the fight or flight response. This response to fear is heightened in those with PTSD.

Q: How are triggers developed?

A: Triggers are developed in response to the sensory details that the brain perceives from a traumatic event. The brain is conditioned to associate the details with the event, which is then seen as a threat by the amygdala.