The science and biology of PTSD

The science and biology of PTSD

Post Traumatic Stress Disorder isn’t ‘all in the mind‘ or something you can just ‘get over’ or ‘move on’ from. No matter how much reasoning and coaxing you do, someone with PTSD or C-PTSD may find it impossible to achieve sustainable recovery without professional treatment.

That’s because Post Traumatic Stress Disorder is a form of injury to the brain. Bringing with it physical as well as mental symptoms and changes.

We feel it’s really important to understand how the brain can change with PTSD and C-PTSD. Brain scans show that PTSD and C-PTSD symptoms and behaviours are caused by biological changes in the brain, NOT by some personal failure. Understanding the changes can also help friends and families gain a better understanding that their loved one’s symptoms are not their fault. This can promote forgiveness and encourages families to become more involved in the healing process.

Modern science has enabled us to get a far clearer picture of the brain and in fact the whole neurological system’s structure and activities. It has become possible to map and measure the different development paths that each human brain follows. Our age and the things that happen to us each day naturally dictate microscopic changes to our brain’s structure.

PTSD Brain Scan
Healthy Brain Scan

This level of investigation has clearly shown PTSD’s impact on the way we think, feel and behave has a physical imprint: markers that you can see on brain scans such as the diagrams here. SPECT (single photon emission computed tomography) is a nuclear medicine study that evaluates blood flow and activity in the brain. It shows three things: healthy activity, too little activity, or too much activity. A healthy “active” scan shows the most active parts of the brain with blue representing the average activity and red (or sometimes red and white) representing the most active parts of the brain. In the healthy scan, the most active area is in the cerebellum, at the back/bottom part of the brain. In the PTSD scan, a diamond pattern of increased activity is evident in the deep emotional part of the brain. The scan from a person with PTSD shows a diamond pattern of increased activity in the deep emotional part of the brain.

The extreme stress and reactions from PTSD and C-PTSD results in acute and chronic changes in neurochemical systems and specific brain regions, which result in longterm changes in brain “circuits,” involved in the stress response. This is why replacing negative connections and cycles, or finding a way to bypass them, can take a heavy investment of time and therapy.

This article looks at the parts of the brain affected by PTSD and C-PTSD.

As a starting point, here’s an important definition. The things that affect our body are referred to as physiological. When it’s our emotions and mental capabilities that are impacted, the word used is psychological.

The two are intimately bound together. This largely revolves around hormonal ‘signals’ and parts of the brain called the amygdala, hippocampus and medial prefrontal cortex.


The amygdala is the part of the brain that formulates a response to stress. It takes this ‘alert’ from sensory input – such as something you see or hear – and connects it to something from your memory.

In response to perceived danger, it sends out an ‘alarm’ to warn the rest of your body that various psychological actions are needed. For instance, that to defend yourself you need to activate flight, fight or freeze.

Once the danger or perceived danger has passed, new signals are transmitted to calm everything back down.

Someone who has PTSD or C-PTSD often has excessive activity in their amygdala, which can be picked up on brain scans.

This is when the amygdala is too sensitive, triggers too easily or stays on high alert for longer than it should. The symptoms would be hypervigilance and an extreme reaction to perceived threats, including being easily startled and often in a state of anxiety.

Having an overactive amygdala creates other physical effects too, including poor sleep patterns.


This part of the brain works in tandem with the amygdala.

It is where we store memories, and also the brain tissue that sorts and retrieves memories.

PTSD or C-PTSD can make this link ‘unstable’.

For example, when someone without the condition hears a loud bang, though it makes them jump, in a split second they make a connection with fireworks and realise one has gone off nearby. The message is relayed to the amygdala that all is well, and it’s appropriate to stay calm.

Someone who has experienced trauma may make the connection to an extremely traumatic incident instead. For example, a firework sends them into a state of anxiety and fear, possibly creating flashbacks and extreme behaviours – their mind thinking it’s someone breaking into their house, a gun shot, a terrorist attack etc. 

In this situation, the hippocampus does not supply the amygdala with the message to calm everything down.

It’s believed that this sort of constant activity can reduce the size of the hippocampus, so again the physical effect of PTSD and C-PTSD can be seen on scans.

Also, re-experiencing the trauma can create other physiological symptoms, such as sweating, insomnia and severe headaches.

Medial prefrontal cortex

The prefrontal cortex – situated around your forehead – deals with emotions and impulses, and therefore has a substantial role to play in your actions.

Under normal circumstances, it would act in tandem with your hippocampus, sending signals to your amygdala to ‘switch off your alarm system’ when a situation calms down. It is like a ‘brake’ system for physical responses to stress, reassuring you that all is well.

When someone has PTSD or C-PTSD, this part of the brain is often underactive. It is ‘dampened down’ by the trauma. This can manifest as someone being withdrawn, irritable and appearing ‘cold’ or showing avoidance behaviours.

It’s an involuntary defence mechanism, creating emotional numbness so you don’t have to relive the intense feelings created by your trauma.

Low activity in your prefrontal cortex (visible on scans) means it doesn’t interact efficiently with your hippocampus and its store of memories and interferes with your amygdala alarm system’s ‘off switch’.

Alternatively, a malfunctioning medial prefrontal cortex could make fear your dominant emotion. This too keeps your amygdala on high alert.

Importantly, the frontal lobe is also the part of the brain that deals with language skills. PTSD or C-PTSD brain injury can therefore result in the individual struggling to articulate their emotions and thoughts.

‘Deranged’ cortisol levels

Cortisol is a stress warning to your body, and therefore it heightens alertness and creates fear.

When your brain ‘decides’ to put your body on full alert, the amount of cortisol produced increases. It can alter or even shut down certain functions, to keep you ready for ‘fight or flight’ for example

When the perceived danger is gone, your brain again adjusts the production of cortisol, calming it down and so allowing the rest of your body to ‘reset’ back to normal.

What happens if this ‘calm down’ message is never issued? Your alarm system is switched on around the clock and your body is continuously in stress mode.

This then impacts on your core bodily functions like digestion and sleep. So can see why elevated cortisol can result in significant physical issues too. Including sleep deprivation, digestive issues, migraines and even heart attacks.

You may also have problems with your moods, memory and concentration. As well as anxiety, or conversely depression.

In some people with PTSD or C-PTSD, they have too much cortisol, and in others, it’s too low. Find our more about cortisol and PTSD here

The perfect storm in your brain

You can see how this creates a ‘perfect storm’ if you have suffered extensive trauma. Your amygdala is over-active – but your system to calm it down is not effective – leaving you continuously or repeatedly in ‘danger’ mode.

Leading to extreme reactions and actions, that to someone else look out of proportion to the situation.

This physiological response to PTSD or C-PTSD can be measured as ‘red hot’ electrical impulses in your amygdala, and a smaller than average hippocampus.

Therapies for Post-traumatic stress disorder will often focus on ‘rewiring’ the connection between your memories, emotions and behaviours. Giving you new associations and coping strategies, to dismantle negative cycles and create healthier brain function.

It’s important to emphasise that everyone’s experiences of PTSD and C-PTSD are individual to them. So, their brain alterations – as well as emotional and behavioural responses – are unique to them too.

However, as we get a better understanding of how the human brain works, it becomes even more apparent that PTSD and C-PTSD makes significant alterations to the brain’s structure and the way it works.

How treatment can work

Understanding how PTSD and C-PTSD alter brain chemistry is critical to understanding the symptoms, devising treatment methods, and to providing the answers as to why some people develop PTSD or C-PTSD from trauma, and others do not.

This diagram shows scans from a ‘PTSD brain’ vs the same brain after treatment.

There is evidence that successful treatment of PTSD with therapies such as EMDR and CBT do produce measurable structural changes in brain regions associated with fear conditioning.

CBT can work by strengthening connections between the amygdala and brain regions that are involved in cognitive control, providing more control of processes that are dysregulated as a result of PTSD or C-PTSD.

EMDR treatment has reported significantly larger hippocampal volumes and changes shown in MRI scans which show connectivity changes affecting bilateral temporal pole structures. 

These studies show why it’s possible to reverse the effects and heal from PTSD and C-PTSD. 

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

  • The Anatomy of PTSD

  • How PTSD Affects The Brain

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  • 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).
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  • 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).
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  • Revisiting the Role of the Amygdala in Posttraumatic Stress Disorder By Gina L. Forster, Raluca M. Simons and Lee A. Baugh Submitted: May 16th 2016Reviewed: January 24th 2017Published: July 5th 2017 DOI: 10.5772/67585
  • Zhu, X., Suarez-Jimenez, B., Lazarov, A., Helpman, L., Papini, S., Lowell, A., Durosky, A., Lindquist, M. A., Markowitz, J. C., Schneier, F., Wager, T. D., & Neria, Y. (2018). Exposure-based therapy changes amygdala and hippocampus resting-state functional connectivity in patients with posttraumatic stress disorder. Depression and anxiety35(10), 974–984.
  • Haochang Shou, Zhen Yang, Theodore D. Satterthwaite, Philip A Cook, Steven E. Bruce, Russell T. Shinohara, Benjamin Rosenberg, Yvette I. Sheline,
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Images and diagrams with permissions from Fallon Jordan at AmensClinic.

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