If it wasn't for a mate showing up to take him fishing, former Australian soldier Damien Irish might not be here.

Key points: Mr Irish suffered PTSD after serving in East Timor and was addicted to weight-loss drugs

Mr Irish suffered PTSD after serving in East Timor and was addicted to weight-loss drugs He is competing at the Invictus Games

He is competing at the Invictus Games A PTSD medical expert says the Games can have a "very powerful" affect on veterans

The 42-year-old veteran was medically discharged from the Australian Defence Force (ADF) for being overweight in 2009, and has suffered from anxiety and depression.

He also had post-traumatic stress disorder (PTSD) from serving in East Timor and became addicted to a weight loss drug.

"It was a very disappointing way to leave the Defence Force I'd loved for 12 years," Irish said.

"A lot of anger issues that I couldn't control and mainly my family sort of copped most of it, which sort of spiralled out of control.

"It took my wife to kick me out of the house and I sort of woke up to myself.

"I wanted to take my own life — the morning I almost committed suicide, if it wasn't for my mate turning up to go fishing, it would have been all over."

Preparing for the games has helped Damien Irish win the battle against his addiction. ( ABC News: Michael Rennie )

Irish is one of the athletes competing in this year's Australian Invictus Games, to be held in Sydney.

Over the weekend, the track and field athletes have been taking part in a training camp in Townsville in north Queensland.

Irish said preparing for the games had helped him work through his addiction.

"It's massive, just being around people, a lot of them have gone through the same struggles that I have, and have the same symptoms, but still that military bond is so much there and after eight years of being out, it's like we're all back in the military again," he said.

"You'll always have a bond — it doesn't matter when you served or who you served with — there's always a bond there."

Fellow veteran and athletics captain Brigid Baker also struggled to adapt to civilian life.

Brigid Baker served with the Australian Defence Force between 2002 and 2017. ( ABC News: Michael Rennie )

The mother of two worked as a medic and intelligence officer between 2002 and 2017 and served in Afghanistan.

It was not until late last year that she was diagnosed with PTSD, anxiety and depression.

She said transitioning to life outside the ADF was tough.

"[In Defence] you become so engrained in your routines and your structures and you're comfortable in the way things occur around you," she said.

"I became very frustrated with the fact that I was very regimented, everything had timings, everything was planned, and it's a little more free-flowing in the civilian world."

Both Baker and Irish will compete in shotput, discus and power lifting.

Brigid said working toward the games helped her transition back into civilian life. ( ABC News: Tom Lowrey )

Invictus Games 'powerful' in fight against PTSD

David Forbes, an international expert in PTSD, agreed the Invictus Games could be "very powerful".

"I think they can give participants and those that are involved in any way a strong sense of agency and control, where they can go beyond being a prisoner of their physical or mental condition, or both," Professor Forbes said.

Professor David Forbes agrees the Invictus Games could be "very powerful". ( ABC News )

"It's often the social isolation that can be the most emotionally painful part of the condition [PTSD], where you feel so cut off from other people.

"So the games also make an effort to bring people together and get that shared sense of experience.

"What's really important is that there's support afterwards and those gains that are made are sustained and that it's not just a wonderful event, you feel very connected and then suddenly you feel very alone again."

The Invictus Games is an international adaptive multi-sport competition for serving and former serving military personnel who have been wounded, injured or become ill during their military service.

Invictus Games 2018 starts in Sydney next month and will attract competitors from 18 nations who will compete in 11 adaptive sports events.