Post-traumatic stress disorder is a physical condition, not a psychological one, a new study claims.
Brain scans reveal veterans who experienced traumatic stress as well as head injuries had different shaped brains from their fellow servicemen who did not suffer PTSD.
Those tormented by their experiences had a larger amygdala - the brain region responsible for emotion and fear - than those that did not.
The findings published by the University of California, San Diego, on Tuesday open the field to explore physiological treatments for the mental illness.
'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,' said lead author Dr Joel Pieper.