Dwayne 'The Rock' Johnson "ripped open" trauma from his past to play MMA star Mark Kerr

Johnson, 53, told Vanity Fair magazine: "You have to be willing to tap into all the stuff that you've gone through, and this was stuff that I had not explored on camera or otherwise.

"I'm not a big therapy person, even though I'm an advocate for whatever it is you need. I found it so scary, but also, so nourishing and freeing. I ripped it open."

The Smashing Machine tells the story of Kerr's rise to fame and his battle with substance abuse, and Johnson - who got to know Kerr during his time as a wrestler - admits the story resonated with him.

He told the publication: "I lost a lot of my friends to addiction and to suicide - in the late '90s, early-to-mid 2000s, there were a lot of untimely, very early deaths."

Johnson added of the nerves he felt taking on the role: "It was very real. I had not experienced that in a very, very, very long time, where I was really scared and thinking, I don't know if I can do this. Can I do this?

"I realized that maybe these opportunities weren't coming my way because I was too scared to explore this stuff."

The Smashing Machine is due for release in October.

It comes after Johnson previously opened up about his tactic for dealing with "screwy or wobbly" moments in life, insisting he tries to focus on the positive.

He told 'Extra': "I think, trying to find joy around every corner, even if things are a little screwy or wobbly, maybe in real life.

"So, I've had a tendency over the years to not sweep it under the carpet but just, I know funky s*** is going on and I'm dealing with it, but let me try and find a place over here where I can be happy or smile or try and access some happy and joy.

"I find myself doing that. It helps me deal with the not-joyous stuff."