Structural Changes

PTSD causes the brain undergoes structural changes similar to that of Traumatic Brain Injury (TBI). The major parts of the brain affected are the amygdala, hippocampus, and medial prefrontal cortex, however, neurotransmitters also undergo changes.

Amygdala

The amygdala is part of the brain’s limbic system, which is known as the emotional center of the brain. The limbic system is not one specific part of the brain, but many parts that act together to create the emotional world of an individual. The amygdala is responsible for the processing of emotions, particularly fear and the emotional significance of events. It plays a crucial role in the body’s fight or flight response and is involved in the formation of emotional memories.

Within the limbic system, the amygdala’s main job is to process fear and stress responses. The amygdala is the smoke alarm of the brain. It is constantly sizing up situations and detecting threat. Most people understand PTSD to be hyperactivity in the amygdala causing flashbacks, hypervigilance, and strong emotional responses to perceived threats. For these cases, the amygdala has become enlarged and hyperactive. An example of this would be a car backfiring causing someone to jump and run down the street, or a small frustration causing an extreme emotional outburst.

The relationship between PTSD and the amygdala is complex, and for a variety of reasons, the amygdala can also become smaller and less active in some people with PTSD, causing them to not respond to fear or react emotionally to things most people would have strong reactions to. An example of this would be someone being robbed at gunpoint but not feeling fear at all, or even having the feeling that they are watching the event taking place rather than experiencing it themselves. For more information on this, see this page here <link to DPDR>.

Hippocampus

Like the amygdala, the hippocampus is also part of the limbic system and is involved in the formation and consolidation of new memories. It plays a critical role in the transfer of short-term memories to long-term memory. PTSD seems to shrink the size of the hippocampus and impair its functioning.

Along with the amygdala, the hippocampus also plays a role in regulating stress hormones like cortisol. In some people with PTSD, the hippocampus may be producing too much stress hormone and in some it may not be producing enough at the proper times.

Medial Prefrontal Cortex and Anterior Cingulate

The medial prefrontal cortex (mPFC) and anterior cingulate cortex (ACC) are two parts of the brain that are physically connected work together. They communicate with the amygdala, hippocampus, and other prefrontal areas to process emotions, cognition, and stress. These regions are also involved in decision-making, goal setting, and socializing.

PTSD can cause a decrease in size and activity to these regions causing impaired emotional regulation, leading to heightened emotional reactivity and symptoms such as hypervigilance and irritability. There is also evidence that the connectivity to the other brain regions can be impaired, leading to further emotional regulation issues.

The mPFC is involved with a process called fear-extinction. Fear extinction is the unlearning of a fear. For example, children go through a stage of being afraid of people they have never met. If we did not have fear extinction, this would never stop and we would constantly be afraid of the people we see on the street. People with PTSD often have impairment to this system. Dysfunction in fear extinction may contribute to the persistence of traumatic memories and heightened fear responses in individuals with PTSD.

PTSD can often be misdiagnosed as ADHD. The reason for this may be from the impairment in the ACC which plays a role in modulating attention, as well as understanding the difference between expected and actual outcomes.

Neurotransmitters

Norepinephrine: Norepinephrine is a neurotransmitter that plays a central role in the body’s stress response. Elevated levels of norepinephrine are often observed in individuals with PTSD. Increased norepinephrine activity is associated with symptoms like hypervigilance, hyperarousal, and an exaggerated startle response.

Serotonin: Serotonin is a neurotransmitter that contributes to mood regulation and emotional well-being. Changes in serotonin function are implicated in mood disorders, and alterations in the serotonin system have been observed in individuals with PTSD. Low levels of serotonin are associated with symptoms like irritability, anxiety, and depressed mo

Gamma-Aminobutyric Acid (GABA): GABA is an inhibitory neurotransmitter that helps regulate anxiety and stress. Changes in GABA function, including reduced GABAergic activity, have been reported in individuals with PTSD. This imbalance may contribute to heightened anxiety and impaired stress response regulation.

Glutamate: Glutamate is an excitatory neurotransmitter that plays a role in learning and memory processes. Dysregulation of the glutamate system is associated with conditions like PTSD. Altered glutamate levels may contribute to difficulties in fear extinction and the persistence of traumatic memories.

Corticotropin-Releasing Factor (CRF): CRF is a neuropeptide involved in the regulation of the body’s stress response. Dysregulation of CRF has been implicated in PTSD, contributing to hyperarousal and exaggerated stress responses.

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