Kit Harington had ''lost his way'' before checking into rehab.

The 'Game of Thrones' star checked into a treatment facility last month after the ending of the hit HBO show - on which he starred as Jon Snow - ''really hit him hard'', and now a costume designer for the programme has said it was clear leaving the show behind affected him, because he was always a ''sensitive soul''.

Michele Clapton told Us Weekly magazine: ''They were children when they started. And it became such an enormous thing, and I think when you stop, it's sort of a huge security blanket is taken away. I mean, they all became friends with each other, and then suddenly, there's nothing to go back to. So I would imagine that had something to do with it. He lost his way a bit.

''He was really a sensitive soul, and he was very upset in that final read through because I think it felt like home for [the cast], and they realised, 'This is it.'''

But the designer is confident Kit will ''be okay''.

She added: ''As much as he's talented and will go on to many other things, I think it's just after eight or nine years, it's a big adjustment. I'm sure he'll be OK, though.''

Kit, 32, checked into Connecticut's Privé-Swiss wellness facility after self-referring himself to the centre last month to work on some ''personal issues''.

His representative said at the time: ''Kit has decided to utilise this break in his schedule as an opportunity to spend some time at a wellness retreat to work on some personal issues.''

And an insider later added: ''The end of 'GoT' really hit Kit hard ...

''He realised 'This is it - this is the end', it was something they had all worked so hard on for so many years. He had a moment of, 'What next?'

''He's in the clinic predominantly for stress and exhaustion and also alcohol.''