Former Olympic swimmer Ian Thorpe has admitted it took him years to be able to discuss his depression and mental health struggles openly.

In a recent interview with Yahoo Lifestyle, the 36-year-old shared that his mental health battle started way back in his teenage years when he was thriving as a professional swimmer and Olympic gold medallist.

“What is on the outside often is very different to what’s going on, on the inside,” Thorpe said. “You can have all of these tremendous successes and all of the trappings that come with success and still not be content, not be happy.

“You actually start to feel a sense of guilt because you realise you should be happy.”

The five-time Olympic champion said at one point he didn’t believe the doctors when they told him his condition was manageable. “I was really struggling,” he said.

“It’s not just being down for that small moment, it’s when you are down and it takes all of your energy to be able to get out of bed or get out of the house. Where you start cancelling plans because you don’t want to see friends, because you’re going through something where you feel, not only sad, but quite hollow during that time. And you’re being entirely irrational in what you’re doing.

“The best thing for you to do is actually to go out with your friends, walk the dog, swim a few laps. But in that time, you just don’t feel like you can do it.”

In 2014, the swimming great was admitted to a rehabilitation facility for depression after he was found disoriented on a Sydney street.

After getting help, Thorpe said things started to look up in the wake of the shoulder surgery he had in 2015. “I was going for a walk, and then I actually went, ‘I’m actually happy!’” he said.

“It was a simple moment, it wasn’t anything that was special. I just actually acknowledged the day that I’m actually happy on this moment. And I have been for a couple of weeks now.”

Thorpe said he now knows what to do when the slump returns. “If I get to that point now where I am feeling depressed, I’m going to take the day for myself and I’m not going to leave the house today,” he said.

“But tomorrow I’m going to get up and do what I have to do that day. And if I can’t, I’m going to call a friend and I’m going to make sure to have dinner with that friend. So I’ve got a respect for what I’m going through, but put a timeline on it.”

Since he admitted his struggles with depression in his 2012 autobiography, This Is Me, Thorpe has continued to work to raise awareness of the issue, collaborating with not-for-profits focusing on mental health such as Young Minds Matter and ReachOut.

“Even though I may at times struggle with depression, I’ve decided I don’t want it to define me,” Thorpe wrote in a blog post in 2016.

“I realise the wonder of the world and I approach each day with an enthusiasm that I haven’t felt for what seems like an eternity.”

If you are troubled by this article, experiencing a personal crisis or thinking about suicide, you can call Lifeline 131 114 or beyondblue 1300 224 636 or visit lifeline.org.au or beyondblue.org.au.