Bryant has worked on many Australian and international projects aimed at reducing PTSD and other mental health disorders following trauma exposure. These include the 9/11 terrorist attacks in New York, the 2004 Asian tsunami, and Hurricane Katrina. For example, he worked with the Thai Ministry of Health to develop a mental health initiative to manage the effects of the tsunami on mental health. Following Hurricane Katrina he was invited to co-develop a mental health protocol for managing disasters in the USA. Bryant adapted his protocol in the aftermath of the major Black Saturday bushfires in Australia, which government authorities adopted as the mental health response to the disaster. In addition, he served on the American Psychiatric Association's DSM-5 Working Group on Traumatic Stress Disorders and the World Health Organisation's ICD-11 Traumatic Stress Advisory Group to develop the new diagnostic definitions of traumatic stress disorders.