Dwayne Johnson felt like he was in a "bubble" when he battled with depression.
The 'Furious 7' star admits he struggled to relate to anyone but over time learned to realise he wasn't alone.
He said: "I found that with depression one of the most important things you could realise is that you're not alone.
"You're not the first to go through it, you're not going to be the last to go through it and often you feel like you're alone and you feel like it's only you and you're in your bubble. I wish I had someone at that time who could just pull me aside and [say], 'Hey, it's going to be okay.'"
The 43-year-old actor also made a public plea to those suffering with the illness to "hold on to that fundamental quality of faith".
Speaking on Oprah's Master Class, he added: "You've just got to remember, hold on to that fundamental quality of faith, have faith, and on the other side of your pain is something good."
One particular source of light in his life is his daughter Simone, 14.
He gushed previously: "I realised being a father is the greatest job I have ever had and the greatest job I will ever have. I always wanted to be a great dad. I always wanted to give Simone things that I felt I never got. I said to her, 'I will always, always take care of you, for the rest of your life. You are safe.'
"Throughout the years, throughout the ups and downs, I've realised that the most important thing that I could do with my daughter is lead our life with love. Not success, not fame, not anything else but, 'I'm always here for you. I love you.'"