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The Neurobiology of Psychological Trauma and Posttraumatic Stress Disorder

The brain is one of the largest and most complex organs in the human body. It is made up of more than 100 billion nerves that communicate in trillions of synapses. The brain is the command center for the human nervous system. As a response to perceived threat, the brain’s sympathetic nervous system promotes the “fight or flight” response. When the threat is over, the parasympathetic nervous system puts a break and promotes “rest and digest”. These systems can become dysregulated after psychological trauma and in individuals who suffer from post-traumatic stress disorder (PTSD).

What is PTSD? According to the Substance Abuse and Mental Health Services Administration psychological trauma can result from experiencing an event, series of events, or set of circumstances that are physically or emotionally harmful or life threatening and that have lasting adverse effects in the individual’s functioning and mental, physical, social, emotional, or spiritual well-being.

Understanding the Neurobiology of Trauma With repeated stress, physical changes in the brain and hormonal imbalances can occur. These are partly the result of neurobiological changes, including the recruitment the hypothalamic-pituitary-adrenal (HPA) axis (Iacona & Johnson, 2018). The HPA axis is the central coordinators in the neuroendocrine stress response systems.

These are the steps of the HPA axis during a stressful event:

  1. The hypothalamus releases corticotropin releasing hormone (CRH)

  2. The anterior pituitary releases adenocorticotropic hormone (ACTH)

  3. ACTH then stimulates the adrenal cortex to release cortisol (the stress hormone).

  4. Cortisol increases body energy, suppresses immune system and suppresses inflammatory response.

  5. As the body senses the cortisol levels increasing and stress levels decrease, the hypothalamus will stop releasing CRH and the body returns to normal. This is called negative feedback

The problem with exposure to trauma is that this HPA axis is being constantly activated. This results in consistently high levels of stress hormones, and chronically affects the immune and inflammatory processes of the body.

Under normal conditions people react to a threat with a temporary increase in their stress hormones, which then dissipate after the threat is over and the body returns to normal. In traumatized people, it takes much longer for the stress hormones to return to normal and spike quickly and disproportionately. Elevated levels of stress hormones can have negative effects on memory and attention, irritability, and sleep disorders. They also contribute to many health issues. After trauma the world is experience with a different nervous system. Unbearable physiological reactions can result in a whole range of physical symptoms including fibromyalgia, chronic fatigue, and other autoimmune disease (Van der Kolk, 2015).

How trauma affects different regions of the brain