For nearly 40 years, Susan Laundy has spent her summers living in terror after surviving two major bushfires that hit her Adelaide Hills property.

Key points: Trauma from Ash Wednesday bushfires only appeared years after the disaster

Trauma from Ash Wednesday bushfires only appeared years after the disaster Children can be especially affected by what they go through

Children can be especially affected by what they go through An expert says tabs need to be kept on victims for a long time after the fire

In 1980, an intense fire saw her running barefoot up a dirt road, trying to escape the flames while herding her horse and six donkeys.

"One donkey doubled back on me — she was so pregnant she could hardly move and I lost her," Ms Laundy said.

"I just kept running and running on foot with the horse.

"You're running on adrenaline and it's only when it all stops that it overwhelms you and you realise what you've been through."

Just three years later, the Ash Wednesday fires came through, bringing the trauma of yet another bushfire.

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While she did not know that she had post-traumatic stress disorder (PTSD), after nearly four decades she sought professional help.

"I just suffered through years and years of hell every summer and I'd sit here and shake because I didn't know what was wrong with me and no-one else knew, so I just suffered alone," she said.

Now, after always staying to defend her property, this summer she has decided to leave on high-risk days, bringing her cats, guinea pig and rabbit with her.

"Listen to the experts — they scared the living daylights out of me back in November on that first really catastrophic day," she said.

"I was terrified and I just thought, if they're telling me it's not safe, they're serious."

The 1983 Ash Wednesday fires in South Australia's south-east. ( ABC )

PTSD takes time to show

The 1983 Ash Wednesday bushfires killed 75 people and burned more than 400,000 hectares across Victoria and South Australia.

Professor Sandy McFarlane, from the University of Adelaide's Centre for Traumatic Stress Studies. ( ABC News: Lincoln Rothall )

Trauma expert Professor Sandy McFarlane studied the longer-term impact of the fires on children, firefighters and the community.

"People in the immediate aftermath are thinking of their survival — they function, they get on with it; the issue is about what you do in the longer term," he said.

He found that decades later, one-third of the children involved in the fires continued to have enduring fears over what they went through.

He is concerned that the infrequent nature of major bushfires meant lessons were often forgotten, but hopes past experience could inform how communities recover after the fires subside this summer.

"There's an enormous concern and outpouring of public sympathy in the weeks and months that follow, but that's not when the most important needs of these communities arise," he said.

"After the Ash Wednesday bushfires, a case register was set up and most people were actually presenting more than two years after the disaster … that's the critical issue, that you plan for the longer term."

He said GPs played a pivotal role in assessing the mental health of people who had been exposed to fire.

"One of the lessons that we learned is that people trust their GPs, they are the people who are already part of that community and they will go and seek their assistance, rather than some health service or counselling service that's been brought in from the outside," he said.

Reassure children of their safety

Professor McFarlane's longitudinal study of bushfire survivors included 800 children across Victoria and South Australia.

His research found that children, like adults, were more likely to show symptoms of bushfire trauma in the years after their exposure.

He also found that in the longer-term, children who had been in the Ash Wednesday fires were less likely to access tertiary education and were more likely to go into relationships early.

"It's almost as though they came to have a slightly constricted view of what the world could offer them because of the fear and the danger they had faced in their childhoods," he said.

The 1983 Ash Wednesday fires burning down the hills behind Clare, north of Adelaide.

His advice to parents of young children was to limit their re-exposure to trauma through supervised access to media.

He also said children needed to be reassured of their safety, and if possible needed to remain with their parents.

"It's important to keep children close to parents," he said.

"People can sometimes think we should get them out of the environment because they will be seeing the destruction and they might be safer away from us.

"Interestingly, it seems children are safer when they are with their parents because if they're not with them, they start to worry about their parents' welfare."

'You carry it with you whether you like it or not'

Andrew Auld was 17 when the Ash Wednesday fires swept through his town of Kalangadoo, in the south-east of South Australia.

While attempting to build a fire break on the family property, the wind changed direction and he was caught in his tractor in the fire front.

He said the heat was so intense, it melted the rubber seals on the tractor door.

"The noise of the fire was like a freight train, the tractor was actually rocking with the wind … one minute it was pitch black and you couldn't see anything, the next minute you couldn't see beyond the glass with a red inferno," Mr Auld said.

While he could not see where he was going, he managed to drive through the fire by using the graded edge on the side of the road as a guide, only to rejoin his family to battle the blaze threatening their house throughout the night.

Mr Auld said he was one of the lucky ones, with nine people in the town, including four children, dying in the fire.

While 37 years have since passed, the heat of Australian summer brings memories flooding back.

"You don't forget what happened," he said.

"The eucalypt smoke is something for whatever reason that sticks in my mind and just the extremes of the weather.

"Every time one of these occurs, and I'm sure all those people who are in the fires now will be the same, it's one of those things that you get to carry with you whether you like it or not."