Learning to get a 600 kilogram horse to move on command may be the unlikely key to helping some war veterans struggling with mental health, substance abuse and homelessness.

The use of horsemanship training as an effective breakthrough for veterans and first responders suffering psychological trauma after a life of service is explored in new documentary The Healing by filmmaker Nick Barkla.

The relationship between horse and human is long-established and celebrated, and equine therapy is becoming a popular alternative treatment.

But former mounted policeman and professional horseman Scott Brodie has set up a charity called Horse Aid where he runs horsemanship training programs with a difference: the human participants are not the only ones struggling as their careers draw to a close.

"There's the parallel between a racehorse and a veteran," Brodie told AAP.

"They've both been trained for a specific purpose and at the end of their careers, pretty much a lot of what they've learnt is superfluous to what they're going to do for the rest of their lives. In fact, negative, to a large extent."

The veterans who attend his courses in the Southern Highlands of NSW - some 190 in the past decade - seem to recognise and identify with the trauma suffered by the horses, he says.

And that desire to help - which is intrinsic to people who have volunteered for a life of service - ends up helping them by giving them a sense of purpose.

The film's director says the magic is in that deeper, intuitive empathy or understanding the veterans have with the animals.

"These horses have come from an institution of racing where they're very regimented ... they're very performance-driven, they take orders and they do what they're told with not a lot of freedom," Barkla said.

"I think in many ways there was a lot of similarity with the veterans.

"There was something about the body language and the breathing, the physical contact, a communication that relies wholly on trust ... within that couple of days, you could see even the body language of the veterans change for the better.

"One of the real powers in that relationship between the horse and the human is that it has nothing to do with words. All these veterans have tried therapy, counselling, and that wasn't what got them breakthroughs in their mental health.

"They love not having to talk about their war trauma. They know what those problems are, they're well-versed. Now they want hope."

Brodie doesn't talk to them about "therapy-type things", Barkla explains. He talks to them about giving the horse a second chance at life and a career, drawing subtle but shrewd parallels with the veterans' own lives.

While he has coached sports teams since he was a teenager, Brodie has never had any training as a counsellor.

"But I'm pretty good at looking at people and seeing what they need and having a feel of what they need to hear at a particular moment," he said.

Sometimes it is as simple as learning to break down a seemingly insurmountable problem into a series of smaller tasks, he says.

"They'll be struggling with a 600 kilo animal in front of them and the tasks they have to carry out, and I'll say 'I want you to try to forget that there's this big horse here'," explained Brodie, who has retrained and rehomed over 500 former racehorses.

"'All you need to do is touch that big object with the whip and make it move to the left'.

"Life can sometimes feel like a whole big mess of things that we've got to deal with.

"Breaking it down into the little tasks you need to achieve can make everything seem a lot easier to deal with."

The Healing premieres in Sydney on October 30 before screenings in cinemas across Australia in November.

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