Post traumatic stress disorder, depression and anxiety can all be quite serious conditions, but it's often difficult to determine who may be prone to developing them. New research suggests that in order to find out, we should perhaps look to a person's skin.

Upon suddenly hearing a gunshot or other loud noise, our bodies respond by sweating, boosting our heart rate, and disrupting our breathing. The response is known as "acoustic startle," and it can be detected with devices such as skin conductance sensors, which measure sweat gland activity in the fingertip.

If that sound is subsequently repeated several times, we begin to get used to it, and that startle response decreases. The speed at which this decrease occurs indicates an individual's level of psychological resilience – the faster that someone habituates to a stressful noise, the higher their resilience.

Previously, studies have suggested that low levels of resilience are associated with both post traumatic stress disorder (PTSD) and depression/anxiety. More recently, scientists from Australia's University of Newcastle and Hunter Medical Research Institute decided to see if those levels could act as predictors of such problems.

Led by Assoc. Prof. Eugene Nalivaiko, they started by questioning 30 healthy young volunteers about their mental well-being, and then subjecting them to skin conductance-based acoustic startle tests. What they found was that in cases where participants' answers indicated a likelihood of developing PTSD or depression, their skin tests likewise indicated low levels of resilience.

It is now hoped that such testing could be used to identify at-risk individuals, hopefully proving more accurate than the currently-used (and somewhat subjective) self-report questionnaires.

"These results will be of particular use to organizations such as Defence, to identify those who may need extra support or increased resilience training," says Nalivaiko. "Eventually, we envisage something like this being of use in schools and other education environments to identify young people who may be particularly vulnerable to psychological stress, so we can ensure the best prevention measures are in place early in their development."

A paper on the research was recently published in the journal PLOS ONE.