His trademark has been his unflappable delivery.

So it is stunning that the 47-year-old father-of-two now reveals that for many years he has suffered almost debilitating anxiety and panic attacks.

Almost to the extent that he thought about walking away from the news industry.

Presenting live television did not cause his anxiety but as his symptoms became more acute over the years - culminating in an internal meltdown while on-air - the popular newsman believed he could no longer do the job he loved.

Then, after years of resistance to the thought of taking medication, he finally opened up to his local GP and was prescribed anti-depressants two years ago.

Those steps have changed his life forever.

"It was like a miracle," he said, as the medication finally gave him some peace and released him from the torturous feeling of being trapped and having no control.

"I was able to function. I could work. I had no fear of going to work anymore."

After 25 years in the media and telling other people's stories, Allen now wants to tell his.

Not to elicit public sympathy, but to let others dealing with mental illness to know that they are not alone.

He wants to contribute to the public conversation about mental illness and help to continue to lift the stigma around it.

Most importantly, he wants to encourage others battling mental illness, especially men, to seek help.

He does it with the full support of his family and of ABC management. ABC TV news editor Eric Napper said there was no question that Allen would continue to read the news Friday to Sunday as well as be on the road reporting during the week.

"He's such an important part of the newsroom and we want to look after him, it goes without question," Napper said.

Allen said he had been battling anxiety for at least two decades but only recently took control of it.

"Looking back now, I can identify my first anxiety symptoms when I was in my early 20s but not knowing what was happening," Allen said.

"And I think that's the case for a lot of people. Unless, they've talked to a doctor or psychologist, they often don't know what's happening to them, because it can be a very physical thing."

Those early symptoms included nausea, low energy, sweating, feeling disconnected from his body and out of control of his actions.

"Probably about six or seven years ago, I had my first panic attack while reading the news and it was crippling, absolutely crippling," he said.

"And, again, I didn't really understand what was happening.

"So for me, I would be reading the news and having these feelings of being totally disconnected from my body, feeling like I was going to faint, almost holding on to the desk. Not being able to breathe properly.

"Classic anxiety symptoms, now that I know what to look for."

While his body was dealing with the internal struggle, Allen never let it show on air.

"I never once stood up and walked out although there are so many times when I wished I could have," he said.

"I think a lot of people will identify with this feeling of being trapped. Whether it's being behind a news desk or walking in a shopping centre or sitting on an aeroplane, they're all forms of anxiety and this feeling that you don't have the ability to get up and move away from the situation."

Allen said most of his colleagues had no idea about his battle.

"It was a very internal struggle for me until I started to experiencing panic symptoms outside of the TV studio and I knew it wasn't related just to my job. This was about my life," he said.

Allen said he had resisted considering medication because he didn't want to feel trapped by a drug. His doctor managed to convince him he should see it as a kind of liberation.

He took six weeks off work to get his body used to the drug.

"That's not to say there aren't some side effects, but for me, it's been an overwhelmingly positive experience," he said.

"And I just can't believe I waited as long as I did to have that conversation with my GP.

"It's not just about medication. It's about whole-of-life management. Not taking your life quite so seriously. Exercising and having hobbies to keep you motivated."

Allen says his condition may have been exacerbated by his job, not least when he had to deliver bad news.

"I'm like any other parent of young children, I hate a lot of the news content. It's not easy to watch some of this stuff. And as a parent, a lot of that actually affected me quite seriously," he said.

"One of the pivotal events was when MH-17 was shot down and I really identified with the plight of those young kids coming home on that flight because we travel with our kids, it so easily could have been us.

"But it was something about that story that really stuck with me. And it made it very difficult to present news on that issue.

"I don't have the luxury of being able to switch off my television or walk out of my room. When you're presenting the news, you're there for the duration."

Allen says he has enormous admiration for then ACT Health Minister Simon Corbell who in 2004 spoke openly about his battle with depression at a time when mental illness was still heavy with stigma.

He wants to be part of the public conversation; to "normalise" mental health conditions.

"One thing I have learnt is that anxiety and stress-related issues are so prevalent," he said.

"When I started opening up about it, I was amazed by how many people said, 'It's funny you mention that because I've had an experience...' So many people. And yet it's not something we talk about openly."

Allen says his experience has made him much understanding of the private struggles of others.

"Sometimes, it's the people who do look really calm on the outside," he said.

"That person at work or in your neighbourhood or that school parent you think has it altogether, sometimes they don't. And it's taught me to be a lot more empathetic to people's problems. You never know what's going on in someone's personal life."

And, in the end, Allen wants to continue in the high-pace world of live news presenting, saying he loved the adrenalin rush, now that he could control it.

"There was a time when it was 'the adrenalin that was your friend is now your enemy' but I have always loved story-telling," he said.

"Sometimes that is tragic news but a lot of times it's constructive news and positive stories and important information to get across."

*Anyone who needs help should ring Lifeline Australia - 13 11 14