Abnormal Psychology: Etiologies of PTSD

What is PTSD?

- anxiety disorder that a person may develop after experiencing or witnessing an extreme, overwhelming traumatic event during which they felt intense fear, helplessness, or horror.

What are some dominant features of PTSD?

- emotional numbing (i.e., emotional non-responsiveness)

- hyperarousal (e.g., irritability, on constant alert for danger)

- re-experiencing the trauma (e.g., flashbacks, intrusive emotions).

Etiologies of PTSD

- abnormalities in the brain, in paticular hippocampus, vmPFC and amygdala.

Hippocampus and Twin Studies

- Low function and volume in the hippocampus is commonly correlated with PTSD symptoms.

- Twin studies can provide an insight as to whether or not the difference in brain structure is a risk factor for PTSD, or a symptom.

Gilbertson et al. (2002): Aim

To investigate whether low hippocampal volume is a symptom or etiology of PTSD.

Gilbertson et al. (2002): Method

- case-controlled study on 34-sets of identical (monozygotic) twins.

- monozygotic twins have 100% of their DNA in common.

- if raised in the same environment they've probably had similar experiences.

- assume that if these twins were then sent to war their hippocampi would be the same in terms of structure and function.

- two different types of identical twins.

- one set of twins, where only one of them has gone to war, and developed PTSD (a trauma exposed twin) and the other twin who hasn't been to war and doesn't have PTSD (trauma unexposed).

- compared with a second set of twins.

- second set of twins is the same as the first, except the twin that went away to war (trauma exposed) did not develop PTSD.

Gilbertson et al. (2002): Results

- trauma unexposed twins of veterans with PTSD had smaller hippocampal volumes compared to unexposed twins of veterans without PTSD.

- MRI results show the correlation between PTSD in veterans and hippocampal volume.

Gilbertson et al. (2002): Conclusion

- important comparison to make here is between the two twins who didn't go away to war (trauma unexposed).

- co-twin of the PTSD patient has a smaller hippocampus compared to the co-twin of the non-PTSD veteran

- suggests that the low hippocampal volume is a factor that increases the vulnerability to developing PTSD as a result of exposure to trauma.

- suggests genetics and hippocampal abnormality are possible etiologies and biological explanations of PTSD symptoms related to memory.

Urry et al. (2006): Aim

Investigated the correlation between the vmPFC and the amygdala during a cognitive reappraisal task using fMRI scanners.

Urry et al. (2006): Method (1)

- 19 participants were exposed to a range of images while they were in the fMRI.

- images were selected carefully so they ranged in ratings of emotional unpleasantness.

- aim of the study was to expose participants to images that would induce an emotional response

- then record their brain activity as they are then instructed to try

- alter their emotional response to the images through cognitive reappraisal.

- reappraisal was manipulated as participants were flashed the images they were told to "increase", "decrease" or "attend".

- participants received training in cognitive reappraisal, so they were able to follow the instructions.

Urry et al. (2006): Method (2)

The strategies they were taught were:

Increase:

- Imagine someone you love experiencing the situation in the image

- Imagine a more intense version of the scene shown in the image

Decrease:

- Think about the situation as being fake or unreal

- Imagine the situation had a better outcome than the one shown

Attend:

- Maintain focus on the stimuli (control condition)

While the participants were performing these cognitive reappraisals, their brain activity was measured.

Urry et al. (2006): Result

Higher activation of the vmPF during cognitive reappraisal to decrease the emotional effect of the stimuli lead to greater reduction of the activity of the amygdala.

Urry et al. (2006): Conclusion

- abnormalities in their vmPFC, they may not be able to perform cognitive reappraisal of affective (emotional) stimuli.

- their emotional arousal generated in the amygdala and the accompanying negative thoughts will persist, keeping their stressful and emotional state high.

- hyperarousal and emotional affect (experiences of negative emotion) are symptoms of PTSD.

Conclusion

- cognitive and biological factors may explain the development and/or expression of symptoms of PTSD.

- Gilbertson et al. (2002) demonstrated that the biological factor

- lower hippocampal volume may result in increased vulnerability in developing PTSD.

- Urry et al. (2006) showed that the cognitive factor of cognitive reappraisal

- decreased the activation of the vmPFC and consequently the effect of an emotional stimulus.

- abnormalities to the vmPFC may affect cognitive appraisal which in turn will lead to symptoms of PTSD.