The veteran sergeant - who had spent 30 years with the Australian Federal Police - could no longer ignore the trauma suffered from decades of searching for dead bodies and chasing child sex offenders.

"I had come back from a shift at the watch house and I just collapsed," he said.

"I looked into [my children's] eyes and they were like big dinner plates. I was crawling and groaning to get to the phone and say I'm not coming into work."

In the previous months he had lost friendships, motivation and decent sleep. That October 2009 morning was rock bottom.

Emergency workers are required daily to show extraordinary resilience. Research shows they face a greater risk of developing trauma-related mental illness compared to the general public. Between 2000 and 2012, 110 Australian police officers, paramedics and firefighters took their own lives.

While working on the frontline is inevitably traumatic, Mr Cunningham believes breaking down stigma and improving support within the police force are crucial to managing the stresses of the job.

No trigger for post traumatic stress disorder is the same; for some it is one horrific incident, for others it is the cumulation of many. For Mr Cunningham, it was his 20 years spent on the police diving squad.

"To feel for a dead body in the dark is a different sensation to anything," he said.

"My mind just became knackered after so much of that stuff."

Mr Cunningham had always been a patient father to his two children. But he found himself regularly snapping for no reason. Then the disturbing dreams started.

"They weren't exactly nightmares, just very vivid dreams."

"I never got enough sleep, I got on medication, I never wanted to do anything."

Since collapsing, he has had multiple stints of mental health leave and doubts he'll ever fully recover.

When asked about internal support, Mr Cunningham said some managers were more supportive than others. He pointed to a psychologist's recommendation to move him into a less traumatic position, that he claimed was unfairly rejected.

The AFP's principal psychologist Patricia Bowden highlighted a range of measures regarding the prevention, identification, early intervention and treatment of trauma-related stress, and said the AFP was always looking to improve awareness and education.

It has annual mental health assessments for "high risk" roles, compulsory mental health training for all staff and both formal and informal debriefing. It is also in the process of rolling out compulsory psychological first aid training and online mental health course.

Nick Arvantis from Beyond Blue, which runs a dedicated police and emergency services mental health program, said most emergency agencies were doing more to improve welfare strategies but poor managerial support remained an issue he observed.

"This can often impact workers as much as the exposure to trauma," he said.

Australian Federal Police Association boss Angela Smith agreed, saying managers failing to act on medical recommendations to move staff between positions was not uncommon.

It was an area Mr Cunningham hoped would improve with heightened awareness of the harm trauma causes emergency workers.

"I know a lot of people carry stuff and don't speak out," he said.

"I hope in the future more will feel like they can."

For help or information, call Lifeline 131 114 or beyondblue 1300 224 636.