The Neurobiology of Trauma

The body’s reaction to traumatic events sets up a number of changes in the brain. When we perceive danger, the limbic system (located in the midbrain, above the brain stem) acts as our internal alarm. When we sense danger, it goes into action and cues the adrenal glands to release stress hormones. These hormones increase blood flow to the major muscles, sharpen our senses, and ready us for a fast response. When the crisis is over, the body eliminates the stress hormones and we go back to normal.

If the trauma occurs early in life and lasts a long time, as in childhood abuse and neglect, the effects are more persistent. The limbic system is primed to remain on alert. With an alarm system stuck on “high,” people impacted by trauma startle easier, have trouble accurately reading faces and social cues, have difficulty sleeping, and tend to avoid situations that increase stress. Since lots of everyday problems increase stress, at least in the short term, problems pile up. Avoidance of difficulties and the emotional pain that accompanies them can lead to phobias and other psychological disorders. (Linehan, 2012).

The thinking part of the brain, the prefrontal cortex, may find it hard to break in and help the limbic system calm down. As well, there may be more activity, as measured by blood flow, to the right prefrontal cortex, which research has shown to be associated with pessimism and depression (Davidson et al., 2003). So, thoughts can get stuck in a rut of ruminating on the past, especially the traumatic past, which in turn keeps the hyperarousal of the limbic system going. 

Evolution designed stress hormones to prepare our bodies to escape from danger. When the crisis has passed and the stress hormones are no longer needed, they are broken down. However, when we are chronically activated, stress hormones become toxic to the brain, interfering with our ability to learn new things and then remember what we have learned. 

The hippocampus, which is part of the limbic system and is involved in organizing memories, is actually smaller in people who have experienced long-term trauma. Cortisol causes cell death in the hippocampus. Given these outcomes, it’s easy to see how problem solving can be difficult (Badenoch, 2008).

People impacted by trauma find it hard to even think things can be better or be aware of moments of well-being. All the little good things in life just slide by their awareness (Hanson, 2009).

Not everyone responds to traumatic events in the classic fight or flight response. Instead, some people’s limbic system shuts the body down. People in a freeze response can become numb and dissociative, and may actually faint when in the midst of a serious crisis (Porges, 2012). This is the unconscious application of the ancient strategy of playing dead so that a predator will lose interest and go away. Losing consciousness is at the extreme end of the freeze response. It is more common for people impacted by trauma to bounce between hypervigilance and dissociation (van der Kolk, 2012).

It is important to remember that these responses to trauma are involuntary. Trauma lives in the nervous system. The body reacts immediately to perceived danger before our thinking brain can accurately name what is going on. These responses are triggered by cues in our daily lives that are associated with the original distressing events. We may not have to look out for actual predators, but loud noises, the look on a loved one’s face, or a hundred other incidents can send people impacted by trauma into a tail spin.

An added difficulty is that many people’s ways of managing negative emotions add to their ongoing tally of traumatic events. Using drugs and alcohol to excess can lead to increased stress from accidents, financial problems, work and school problems, unsafe sex, and unhealthy relationships. These circumstances continue to change our bodies and the structure and function of our brains. As mentioned earlier, the hippocampus grows smaller when chronically exposed to stress hormones. But these same hormones increase the size of the amygdala, creating a feedback loop that makes the limbic  system even more sensitive to environmental cues and internal body sensations associated with trauma. 

It is also important to consider when things are going well and the functions of an “Integrated Brain,” which include:

  • Body awareness
  • Able to attune to others
  • Balanced emotions (neither chaotic or rigid)
  • Able to calm fears
  • Able to pause before acting
  • Capable of insight and reflection
  • Able to feel empathy
  • Capable of having a sense of morality, fairness and the common good
  • Able to be intuitive (Siegel, 2010)

Chronic stress compromises immunity. It becomes more difficult to ward off illnesses. The ACE study, which examined the histories of thousands of patients in California, found that those who reported more adverse events in childhood were also much more likely to suffer from serious illness (Felitti et al., 1998).

Other factors, such as social status, also play a significant role by adding to a person’s sense of being unworthy and discounted by the society in which they live (Baer, 2012). Even more egalitarian cultures that strive to make access to health care universal have difficulty lessening the stigma of poverty’s impact on morbidity and mortality (Sapolsky, 2005).

Health and Social Risks Associated with Ace

Health Domains Conditions associated with ACEs
Medical Conditions Heart, lung, liver diseases, cancers, sexually transmitted diseases, and skeletal fractures
Risk Factors for Common Disorders Smoking, alcohol abuse, illicit drug use, promiscuity, obesity, poor self-rated health, high perceived risk of AIDS
Behavioural Health Depressive and anxiety disorders, PTSD, eating disorders, substance abuse, personality and dissociative disorders, hallucinations, suicide
Sexual and Reproductive Health Early age at first intercourse, sexual dissatisfaction, teen pregnancy, unintended pregnancy, teen paternity, fetal death
General Health and Social Problems High perceived stress, poor job performance, relationship problems, spouse with alcoholism

(Jeannie Campbell, Executive Vice President, National Council for Community Behavioural Healthcare, 2012)

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