PTSD and the Neurobiological Basis of Trauma

Illustrated by Shelly Xu

Trauma is more common than you would think, and it encompasses events and experiences that impact a person’s integrity and well-being. The World Mental Health Survey estimates that around 70 percent of people will experience at least one traumatic incident in their lifetimes [4]. These events can be related to natural disasters, war, sexual or intimate partner violence, or other accidents/injuries [4]. The way an individual’s traumatic experiences manifest can vary significantly; thus, mental health advocates work to raise awareness by communicating that trauma can lead to differential emotional, physical, and behavioral adjustments. Through investigating these behavioral variabilities, researchers have begun to develop theory and foundational knowledge on the physiological results of trauma. It can be all too easy to dismiss the experiences leading to emotional instability as ones to “just get over,”; however, new fields of study on the brain and body of traumatized individuals show that emotional injuries and physical injuries are well connected.

The identification of Post-Traumatic Stress Disorder in the 1970s following increased “psychological and social difficulties of the nearly three million veterans who had fought in Vietnam” acknowledged trauma’s pervasive effect [4]. Yet, almost 50 years passed until the DSM-5 updated PTSD’s narrow definition in 2018 to include three subcategories: reexperiencing, avoidance and hyperarousal [4]. These include intrusive thoughts of the trauma, presence of strategies to minimize the harm caused by the event and extreme startle or hypervigilance. Additionally, while PTSD diagnoses are commonly given to war veterans, psychologists have recently identified survivors of sexual assault and prolonged intimate partner violence (IPV) also frequently suffer from PTSD,  with symptoms of “intrusions, nightmares, startle reactions, and numbness” [4]. The most striking outcome of recent psychology research regarding PTSD is the incidence rate. According to the National Comorbidity Survey Replication, “lifetime PTSD prevalence rates are 3.6 percent and 9.7 percent respectively among American men and women” and are even higher for individuals in post-conflict nations like Cambodia (28 percent) and Algeria (37 percent) [3].  Since PTSD was identified, more extensive research has led to a more detailed diagnosis and an awareness of the high incidence rate. While not all trauma leads to a diagnosis of PTSD, the newfound understanding of the etiology of PTSD have shown researchers that all forms of trauma have far reaching consequences on mental and physical health.

One of the hallmarks of trauma response is the “freezing” response that occurs when someone is unable to move physically or make self-benefitting decisions during a traumatic event. This is due to the activation of the brain’s “fear circuitry,” where neurons in the amygdala (fear center of the brain) are hyperactivated while neural pathways in the prefrontal cortex (center for behavior, higher functional thinking and memory) are inhibited. In this way, fear “takes over” and survivors may experience “tonic immobility,” furthering their inability to escape potentially dangerous situations [5].

In support of these hypotheses, fMRI analysis demonstrates decreased activity in both the hippocampus and the dorsolateral prefrontal cortex, brain regions that are responsible for encoding memories and temporally understanding experiences respectively. “When those brain regions are deactivated, people … become trapped in the moment, without a sense of past, present or future” [1]. When the hippocampus is deactivated, memories are fascinatingly encoded physiologically differently in the brain. This can serve to explain why most of the peripheral details of particular traumatic experiences are unattended to (such as the timeline of events or the happening in the surroundings) leaving individuals with difficulty in explaining the situation as it occurred.

Yet another effect of a decreased activation in the prefrontal cortex is the behavior that occurs when decisions are not made. These behaviors are survival reflexes that occur as a result of habituation or “auto-pilot” in a way that the person dissociates from their experiences [5]. In PTSD and other continuous consequences of trauma, “the overwhelming [traumatic] experience is split off and fragmented… and the sensor fragments of memory intrude into the present” [2].In this way, one may be not only hazy about the order of events that occur during a natural disaster, for example, but also seem disconnected from their experiences when explaining to others. 

With the frontal lobe at the seat of decision making, higher order thinking and experience interpretation, the deactivation of its cognitive processing during periods of  perceived danger creates a plethora of tangible consequences. The research on the biological basis of trauma response has allowed healthcare providers and even the general public to further their understanding that behavior post-trauma is not an individual inherent weakness but rather a biological response to external etiological experiences. These affect not only a person’s comprehension of the experience they went through but also often dictate how this experience will be interpreted for years to come.

Edited by Alexandra Dram
Illustrated by Shelly Xu

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