Post traumatic stress disorder and the circadian system

Post traumatic stress disorder is an unrelenting response to a stressful event(s). While the initiating event resolves, the person’s heightened response to that and future stressors continues well after. This creates consequences that negatively impact the individual’s life.

Many factors go in to a person’s susceptibility to post traumatic stress disorder including:

  • Genetic factors
  • Early environmental factors
  • The current stress load on the individual

Upon exposure to a sufficiently stressful event or events, activation of the stress system initiates what is normally a beneficial response. Under normal conditions you turn on the stress response, the stressor resolves, and the stress response shuts off.

But in those susceptible to PTSD, the stress response remains activated. Furthermore, sensitivity to stress increases making other stressful events generate a significantly larger response.

A recent review developed a new model of how the important factors contributing to post traumatic stress disorder work. This blog briefly covers this study and how the model works.

Post Traumatic Stress Disorder model

The path to post traumatic stress disorder

The image above comes from Multilevel Interactions of Stress and Circadian System: Implications for Traumatic Stress in the journal Psychiatry. It points to 3 main contributing factors that lead down a path of PTSD:

  • Predisposing factors
  • The triggering traumatic event
  • Acute disruption of the circadian cortisol rhythm

We’ll break these down stage by stage.

Predisposing factors

Factors that predispose someone to PTSD include genetic susceptibility, cacostatic load, and early life environment. These factors essentially converge to make a person more or less susceptible to stress

Genetic Susceptibility

Genetic factors play a role in a person’s susceptibility to stress. In addition to gender, polymorphisms in the circadian system(CS-related) as well as the stress system(SS-related) make a person’s HPA axis more responsive to stress. In other words, it gives some people a hair trigger while other people let everything roll of their back.

Cacostatic load

Cacostatic load refers to the stress load on the individual. In other words, the cumulative toll of different stressors a person is currently under. This refers to:

  • External physical stress such as occupational workload, exercise, or injury
  • Psychological stress such as deadlines, bills, and relationship problems
  • Internal physiological stress such as Type 2 diabetes, hypertension, intestinal permeability, or chronic inflammation

Furthermore, some stressors cross categories. For example, circadian disruption is normally due to external factors, but causes internal stress as well. Additionally, the sleep deprivation that comes with it typically does the same.

Early environment

Another huge factor recently grabbing attention in the PTSD realm is early developmental environment. This includes:

  • Prenatal stressors while in the womb
  • Early life trauma
  • The development of coping strategies when young
  • Pre-existing conditions such as autism, mood disorders, diabetes, etc.

Genetic factors, cacostatic load, and early environment all contribute to a person’s susceptibility to post traumatic stress disorder. This underlies the complexity of PTSD. It’s not simply exposure to a stressful event that matters, one must be susceptible to PTSD.

Traumatic stress-A triggering event

When a person who is susceptible to PTSD experiences a stressful event, they may meet the criteria for it. However, we’re repeatedly exposed to stress everyday, so it’s not just a matter of being exposed to stress.

For a triggering event to push a susceptible individual in to PTSD, it must be sufficient to trigger PTSD. Important factors include:

  • The timing of the stress
  • The type of stress
  • The intensity of stress
  • How chronic the stress is

A mild intermittent physical stressor may not be sufficient enough to trigger PTSD. But if that stressor is at the wrong time and promotes chronic psychological stress, it may increase the cacostatic load to the point where the person is more susceptible.

For example, if a person is in a car accident and suffers a broken leg, it may not trigger PTSD. But if the person in the other car dies or the accident puts the person in a poor financial situation, it may eventually meet the criteria to trigger PTSD.

Additionally, certain types of stress cause bigger stress responses at different times. For example, acute physical and psychological stress exerts a larger effect at night than it does the day.

Acute chronodisruption

Once a person who is susceptible to PTSD experiences a triggering event sufficient enough to trigger PTSD, they experience acute circadian disruption. This is due to alteration of the circadian cortisol rhythm, which is a major part of the stress response.

Both circadian and sleep disruption have amplifying effects on the person’s already hypersensitive stress response. Emotional processing is dependent on proper sleep, and circadian rhythms regulate sensitivity of the stress response.

Of course, this is where the genetic polymorphisms in circadian genes mentioned earlier come in to play. Fortunately, this isn’t a life sentence, it simply means an effort should be made to practice good circadian habits.

If an effort is made to re-establish circadian rhythms, the circadian disruption is acute and the person can re-establish health. However, if the circadian disruption persists and remains chronic, healing is prevented and other chronic conditions such as Type 2 diabetes and hypertension accumulate.

Mark and his 35 years of Insomnia

This model explains a lot with regard to PTSD and what we need to do to treat it. Late last year I published a case study on the blog about a gentlman named Mark. It seems like Mark may be a model case.

Mark suffered with chronic insomnia for 35 years, not falling asleep until 4am and wanting to sleep until 4pm. Coupled with this came chronic pain, dysautonomia, muscle imbalances and food intolerance. You can check out his full story by clicking here.

For Mark, there are 2 potential triggering events. He had a months-long bout of viral infection and a bad bike crash with spinal trauma. These events pushed him down a path where chronic circadian disruption kept him in this disease cycle for 35 years.

Correcting the circadian disruption fixed his sleep problem. Within a couple weeks his body experienced what he calls a “total reboot”. His food intolerances also faded and his tolerance for physical activity dramatically increased.

All in all, Mark’s story fits this model perfectly. We never dug in to his genetic susceptibility, but he has spent the last year building resilience so that it never happens again. It’s not hard to imagine how the experiences of people in the military or from traumatic backgrounds can get caught in the same cycle.


Post traumatic stress disorder can take a massive toll on a person’s health and well-being. There is evidence that people with PTSD experience chronic, persistent circadian disruption in their cortisol rhythm.

A recent review puts forth a model for the development of PTSD. At the top level, a person’s susceptibility to PTSD is determine by their genes, current stress load, and early developmental environment. When exposed to a traumatic event or events of sufficient type, intensity, and exposure time, this triggers acute circadian disruption.

If the circadian disruption remains chronic, someone with PTSD is trapped in a cycle of a perpetually heightened stress response. Unless attempts are made to correct the circadian disruption, this will persist.

Mark is a prototypical example of how this model works and can be used to address PTSD. He was able to do this by changing his behavior and practicing good circadian habits.

In the review mentioned above, the authors discuss pharmaceutical options if the lifestyle factors aren’t sufficient. I suggest you check it out, as it goes in to excellent depth on the topic.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.