The science and biology of PTSD

In the study of Post Traumatic Stress Disorder it’s important to understand that PTSD is considered to be a psychological injury rather than a mental illness.

Neuroanatomical studies have identified changes in major brain structures of those with PTSD — the amygdala and hippocampus – showing that there are significant physical changes within the brain as a result of trauma.

These brain changes from PTSD, particularly if not diagnosed yet, can make life seem very confusing, and understanding your own mind can become almost impossible.

  • A PTSD sufferer may struggle to find the right words to express what they are thinking and feeling. This is due to the prefontal lobe (responsible for language) being adversely affected by trauma and so disrupts its linguistic function.
  • People with PTSD can find it hard to control their emotions as the amygdala (responsible for emotional regulation) is in overdrive, due to its increase in physical size.
  • Short term memory loss can also affect those with PTSD as the hippocampus (responsible for memory and experience assimilation) actually shrinks.
  • PTSD can make you feel frightened no matter what you’re doing – your medial prefontal cortex is responsible for this (its role is to regulate emotion and fear responses) as it can’t regulate itself or function properly after trauma.

Effect of trauma specifically on the hippocampus

Under normal conditions, when a memory is built or retrieved, the hippocampus blends together all the elements of a memory from all the sensory areas. Initially, short-term memories are stored in the hippocampus, but when they are no longer required as ‘conscious memories’, the hippocampus processes these into other parts of the brain (to create longer term memories).

As mentioned above however, the hippocampus tends to reduce in volume in those with PTSD and so the recording of new memories and retrieval of older memories in response to specific and relevant environmental stimuli can become distorted.

The hippocampus is also responsible for distinguishing between past and present memories, and so those with PTSD can lose the ability to discriminate between past and present experiences (resulting in flashbacks).

Effect of trauma specifically on the ventromedial prefrontal cortex

The ventromedial prefrontal cortex region of the brain regulates negative emotions (such as fear).

Due to this region shrinking in those with PTSD, the ability to regulate these emotions is reduced – causing fear, anxiety, and extreme stress responses even when faced with things not connected – or only remotely connected – to their original trauma.

Effect of trauma specifically on the amygdala

Trauma has been shown to increase activity in the amygdala region.

This region of the brain helps us process emotions, and is also linked to fear responses. It uses the hippocampus to query situations from the past to ascertain answers to questions such as ‘Is this safe’, ‘Do I like this’ and most significantly in PTSD ‘Do I need to start up the stress responses and trigger hormones’. As you may imagine, if this region of the brain is hyperactive, and is connecting with an already ‘broken’ hippocampus, the effects it will have on our emotional regulation will be a distorted view of a situation.

Studies have shown that PTSD sufferers exhibit hyperactivity in the amygdala in response to stimuli that are connected to their trauma – however, the amygdala is so hyperactive in some patients that they exhibit fear and stress responses even when they are ‘simply shown photographs of people exhibiting fear’.

Effect of trauma specifically on Cortisol Levels

The biologic alterations observed in PTSD do not uniformly resemble those associated with other types of stress. For example, cortisol levels have been lower than normal in some studies of patients with PTSD, however corticotropin-releasing factor in cerebrospinal fluid appear to be increased.

This pattern differs from the patterns associated with brief and sustained periods of stress and with major depression, which are typically associated with increased levels of both cortisol and corticotropin-releasing factor.

These psychological and biologic data supports the hypothesis that the development of PTSD is facilitated by a failure to contain the biologic stress response at the time of the trauma, resulting in a cascade of alterations that lead to PTSD.

Furthermore, it has been shown that patients with chronic PTSD have even more increased circulating levels of norepinephrine and reactivity of adrenergic receptors. These alterations, in addition with the findings that thyroid hormone levels are generally increased in patients with PTSD, also explain some of the somatic or physical symptoms of the PTSD.

Understanding how PTSD alters brain chemistry is critical to empathizing with the symptoms of PTSD, devising treatment methods, and to providing the answers as to why some people develop PTSD from trauma, and others do not.


If the full science details seem to complex, we’ve written a simpler science based blog post here: Understanding PTSD if you’ve seen Pixars’ Inside Out

SOURCES:  POST-TRAUMATIC STRESS DISORDER , The New England Journal of Medicine, 108 · N Engl J Med, Vol. 346, No. 2 · January 10, 2002 , RACHEL YEHUDA, PH.D, Post Traumatic Stress Disorder What Happens in the Brain? Sethanne Howard and Mark W. Crandall, MD US Naval Observatory, retired, Wash. DC Reisterstown, Maryland, Brain Blogger, Heal my PTSD, Bremner JD (2006). Traumatic stress: effects on the brain. Dialogues in clinical neuroscience, 8 (4), 445-61 PMID: 17290802, Bremner JD, Elzinga B, Schmahl C, & Vermetten E (2008). Structural and functional plasticity of the human brain in posttraumatic stress disorder. Progress in brain research, 167, 171-86 PMID: 18037014, Hull AM (2002). Neuroimaging findings in post-traumatic stress disorder. Systematic review. The British journal of psychiatry : the journal of mental science, 181, 102-10 PMID: 12151279, Koenigs, M., & Grafman, J. (2009). Posttraumatic Stress Disorder: The Role of Medial Prefrontal Cortex and Amygdala The Neuroscientist, 15 (5), 540-548 DOI: 10.1177/1073858409333072, Nutt DJ, & Malizia AL (2004). Structural and functional brain changes in posttraumatic stress disorder. The Journal of clinical psychiatry, 65 Suppl 1, 11-7 PMID: 14728092, Rocha-Rego, V., Pereira, M., Oliveira, L., Mendlowicz, M., Fiszman, A., Marques-Portella, C., Berger, W., Chu, C., Joffily, M., Moll, J., Mari, J., Figueira, I., & Volchan, E. (2012). Decreased Premotor Cortex Volume in Victims of Urban Violence with Posttraumatic Stress Disorder PLoS ONE, 7 (8) DOI: 10.1371/journal.pone.0042560, Shin LM, Rauch SL, & Pitman RK (2006). Amygdala, medial prefrontal cortex, and hippocampal function in PTSD. Annals of the New York Academy of Sciences, 1071, 67-79 PMID: 16891563


Share Page