The Game of Thrones star told The Sunday Times that he is sober after a "huge fundamental change in who I was and how I went about my life".
Harrington recently became a father after he and his wife, actress Rose Leslie, gave birth to their first son.
"I have a child and my relationship is brilliant," Harrington told The Sunday Times.
“I’m a very, very happy, content, sober man.”
“Things that have happened to me since Thrones ended, and that were happening during Thrones, were of a pretty traumatic nature and they did include alcohol," he added.
The actor also revealed that he'd struggled with suicidal thoughts: “I went through periods of real depression where I wanted to do all sorts of things.”
According to Harrington, the thoughts made him feel "bad" and "shameful" : “And getting sober is the process of going, ‘No, I can change’.
“One of my favourite things I learnt recently is that the expression ‘a leopard doesn’t change its spots’ is completely false: that a leopard actually does change its spots.
“I just think that’s the most beautiful thing. It really helped.
“That was something I kind of clung to; the idea that I could make this huge fundamental change in who I was and how I went about my life.”
The actor added that fatherhood is “the most physically draining thing”.
“My hat goes off to any single parent,” he said.
“Any single parent, you’re a f****** genius. I don’t know how you do it.
“Because it’s more exhausting than everything I did on Thrones.”
