Post-traumatic stress disorder (PTSD) has always been associated with mental health, but new research suggests there's a physical aspect to it too – that a certain area of the brain is larger in people suffering from PTSD.

That means we could improve the way we detect and treat the debilitating condition by looking at physical as well as psychological signs, giving doctors something outside the mind that they can study.

The research focussed on the left and right amygdalae, those parts of the brain that control our fearfulness and how we respond to outside stimuli that could be seen as threatening or dangerous. The amygdalae also have a big role to play in the way we make decisions and process memories.

"Many consider PTSD to be a psychological disorder, but our study found a key physical difference in the brains of military-trained individuals with brain injury and PTSD, specifically the size of the right amygdala," says one of the team, Joel Pieper from the University of California, San Diego.

"These findings have the potential to change the way we approach PTSD diagnosis and treatment."

The team scanned the brains of 89 current or former members of the military with mild traumatic brain injury, with 29 of those also diagnosed as having significant PTSD as well.

When the researchers looked at those 29, they found their amygdalae were about 6 percent larger – particularly on the right side – compared with the participants who weren't affected by PTSD.

No major differences in age, education, or gender were found between those with PTSD and those without.

"We wonder if amygdala size could be used to screen who is most at risk to develop PTSD symptoms after a mild traumatic brain injury," says Pieper. "On the other hand, if there are environmental or psychological cues that lead to brain changes and enlargement of the amygdalae, then maybe such influences can be monitored and treated."

Before we get ahead of ourselves, the researchers note that more research is needed into the relationship between PTSD and amygdala size: the research only shows association and doesn't prove that PTSD causes changes to the amygdalae.

What's more, the brain injuries of most participants in this study were caused by blast injuries, so different injury types – such as those caused by sports concussions – may have different effects on the brain.

Even with those limitations though, the researchers describe what they've found as an "intriguing structure-function relationship", especially considering the links between fear and memory and the amygdalae.

The research follows a 2016 study that found some limited evidence of a link between PTSD and damage to brain tissue in blast victims, suggesting there might be other physical after-effects that go hand-in-hand with PTSD.

Around 7.7 million people over the age of 18 are believed to suffer from PTSD in the US, and it can develop from any type of traumatic episode, from witnessing a natural disaster to serving on the front line.

Let's hope scientists can figure out better treatments for the condition as the physical aspects of PTSD are more fully understood.

The findings have yet to be published in a peer-reviewed journal, but have been presented at the American Academy of Neurology's Sports Concussion Conference.