Shocked eyes reliving trauma

It is believed that your eyes give you away; they are a window into your soul. Indeed, it is difficult to pretend with the eyes—they reveal the truth of your emotional state, despite what you say or how much you deny.

This belief just got a shot in its arm. New research shows how a person’s pupils respond to threatening images reveals if they have suffered a traumatic experience in the past.

The research, led by Dr Aimee McKinnon at Cardiff University and published in the journal Biological Psychology, looked for traces of these traumatic events in the eyes of patients suffering from post-traumatic stress disorder (PTSD). They measured the pupil of the eye while participants were shown threatening images such as vicious animals or weapons, as well as other images that showed neutral events, or even pleasant images.

When you experience a traumatic event such as a car crash, combat stress, or any kind of abuse, it can lead to PTSD and can leave you with a greater sensitivity, or hyperarousal, to everyday events and an inability to switch off and relax.

The response of those with PTSD was different compared to other people, including those who had been traumatised but did not have PTSD.

Positive and negative stimuli

During the experiment, at first the pupils failed to show the normal sharp constriction that is caused by changes in light level—but then their pupils grew even larger to the emotional stimuli than for the other participants.

What’s more, the exaggerated response of the pupils of patients with PTSD was not limited only to threatening stimuli, but also to stimuli that depicted positive images, such as exciting sports scenes.

Professor Nicola Gray believes this is an important finding. Gray, who is from Swansea University, co-authored the paper along with Professor Robert Snowden of Cardiff University. She said, “This shows that the hyper-response of the pupil is in response to any arousing stimulus, and not just threatening ones. This may allow us to use these positive pictures in therapy, rather than relying upon negative images, that can be quite upsetting to the patient, and therefore make therapy more acceptable and bearable. This idea now needs testing empirically before it is put into clinical practice.”

A tremendous burden

Dr McKinnon, who is now at Oxford University, believes that being primed for threat and fear responses in any uncertain emotional context is a tremendous burden those who have PTSD.

He added, “It also suggests that it is important for us to recognise that, in therapy, it is not just the fear-based stimuli that need deliberately re-appraising.

“If someone with PTSD is faced with any high-level of emotional stimulation, even if this is positive emotion, it can immediately trigger the threat system. Clinicians need to understand this impact of positive stimuli in order to support their service-users overcome the significant challenges they face.”


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