Kit Harington has revealed he was diagnosed with Attention Deficit Hyperactivity Disorder (ADHD) while in rehab for alcohol issues in 2019.

The 37-year-old actor - who has two children with wife and 'Game of Thrones' co-star Rose Leslie, 36 - revealed he was shocked to receive the diagnosis in an American rehab clinic, after years of trying to get sober.

In a trailer for new podcast 'The Hidden 20 per cent', with Autistic and ADHD entrepreneur Ben Branson, Kit said: "I went to a rehab in America, they identified me as being ADD."

According to The Times newspaper, Kit said about his alcohol dependency: "The trouble was then it wasn’t just socially. I loved nothing more than drinking alone because it took me out of myself, took me out of that headspace, took me out of that anxiety instantly."

He spoke about his struggle with fame after starring as Jon Snow in 'Game of Thrones', saying: "People would treat me like the character, who was a hero and good. But in my life, personally I didn’t feel like that at all. And that, I think, [led to] some kind of psychological scarring. I was drinking a lot. I was going through addiction and everything that entails and hiding things and all sorts. And that was the polar opposite of the character I was playing, who couldn’t tell a lie.”

After he finished filming 'Game of Thrones' he had a “kind of a breakdown, where it all got too much”.

Things escalated when he played an alcoholic in Sam Shepard’s play 'True West' in London in 2018-19.

He said: "[The] character and me did get very mixed up at that point. I didn’t know who I was, really. Continually drinking while playing an alcoholic. It was at its worst. It was during that play that I sort of collapsed and told people around me what was going on and finally took action."

This was his second stint at rehab, after he previously quit one four years earlier.

He said of his first attempt: “I entered rehab drunk, sobered up in there and went, ‘Ah... not you guys in a circle. No, thank you.’ And I left that pretty quick and said, ‘I’ll try to deal with this by myself.’ Which didn’t work after about four years.”

However, this time: "I saw that my life was hinging on this. Luckily it was the right place at the right time. I managed to forge a new life from there.”