Post-Traumatic Stress Disorder (PTSD)




What is Post-traumatic stress disorder (PTSD)?

Post-traumatic stress disorder (PTSD) is an anxiety disorder that may develop after an event where a person is exposed to actual or threatened death, serious injury, traumatic childbirth or sexual violence. PTSD is defined by symptoms of re-experiencing, avoidance and sense of threat.

What causes Post-traumatic stress disorder (PTSD)?

Neuro-Cognitive Mechanisms of PTSD

Our brains are designed to respond to threat to ensure our survival. The easiest way to understand this would be to imagine yourself deer hunting.

The deer hears the noise of the hunter’s footsteps, lifts its ear, stands still and focusses (orientation to stimuli, selective attention). The next few moments are used to weigh up the danger, to do so, the deer has to prevent the automatic response of running away (response inhibition) but also maintain composure and allow its working memory to check the pros and cons of running, whilst doing so it has to focus hard and not get distracted by other peripheral thoughts (cognitive inhibition). But this process should happen very quickly or else it will get shot (good processing speed and cognitive flexibility/set shifting) finally an ability to learn from each such occasion and encode it efficiently for retrieval, the next time it happens (learning and memory). Excessive allocation of attention towards threatening stimuli might interfere with other neurocognitive processes such as learning and memory. For example, excessive threat perception and anxious reaction by the deer would mean, less efficient retrieval of spatial memory of the forest, resulting in failure to run away from danger effectively. Hence a deficit in any of these steps or its associated cognitive processes makes the deer vulnerable to potential danger. Now imagine an individual feeling the same as the deer being hunted down, when there is no real hunter!

Why would some individuals perceive threat more than the others?

Some factors are known to predispose individuals to increased threat perception, such as:

  • Low general intelligence
  • Reduced ability to set shift as seen in those with perfectionism/rigid thinking / ASD
  • Poor response inhibition as seen in those with ADHD
  • Low verbal memory
  • Neuroanatomical factors

For example, some researchers suggest that persistent re-experiencing and hyper arousal symptoms following trauma may be related to deficits in inhibitory and attentional control. This make it more difficult for individuals to disengage from both internal (e.g., memories) and external (e.g., reminders) threatening stimuli. CBT seem to improve the deficits response inhibition and avoidance, thus breaking this cycle.

Ehlers and Clark’s cognitive theory talks about biased appraisals about the traumatic event, which then lead to selective recall of information that is consistent with these appraisals. Hence those with better cognitive flexibility tend to respond better to CBT as they are able to identify these errors in thinking and rectify it.

Trauma memories that are poorly integrated into other autobiographical memories contribute to negative appraisals of self. Studies have suggested that more proficient memory processes are associated with reduced risk of developing PTSD.

Neuroanatomical factors

Twin studies put forward that reduced activation of medial prefrontal cortex (regulation of limbic system) is a vulnerability factor for PTSD and that this could be an inherited trait. Similarly reduced hippocampal volume(memory) and anterior cingulate volume(attention)could be other inherited factors.

What is complex Post- Traumatic Stress disorder (CPTSD)?

Some individuals with PTSD also have another cluster of symptoms such as affective dysregulation (e.g., emotional reactivity), negative self-concept (e.g., low self-worth) and interpersonal problems (e.g., fear and avoidance of relationships. These additional symptoms have typically been captured by making additional diagnoses of Borderline Personality Disorder, Dysthymia or Major Depressive Disorder and Social Phobia respectively.

What happens to the brain after developing PTSD?

PTSD erodes neurocognitive integrity and is associated with increased risk of cognitive decline. There is evidence that attention and memory processes are vulnerable to the effects of PTSD. These neurocognitive findings are supported by alterations in the brain structures such as frontal cortex, hippocampus, and associated networks. On the other hand, improvement in PTSD symptoms with treatment improve connectivity in the circuitry thereby improving neurocognitive performance.

How is PTSD diagnosed?

PTSD is a diagnosed based on the cluster of symptoms that one may have. A psychiatrist with expertise in PTSD may sit down with you and go through a set of symptoms and its context, followed by a mental status examination before coming to a conclusion. As most individuals with trauma find it hard to openly speak about trauma, this process is done with utmost sensitivity and is usually guided by the individual’s level of comfort.

Are there any brain scans or tests for PTSD?

Although there is a clear neuro-biological basis for PTSD, routine diagnosis does not require brain scans or neuro-psychological tests. Moreover, such tests may not detect any abnormalities even in those who are clinically diagnosed with PTSD (poor sensitivity). Some of the brain abnormalities are shared by other disorders such as depression and schizophrenia (poor specificity). Hence, routine diagnosis of PTSD is made clinically, following a set of diagnostic criteria such as DSM V or ICD 10.

References: S.B. Sartori, N. Singewald / Pharmacology & Therapeutics 204 (2019) 107402