"Bodyguard" star Richard Madden said playing the role of a war veteran with post traumatic stress disorder in the hit BBC series took a toll on him.
The 32-year-old portrayed David Budd who is assigned to protect controversial politician-home secretary Right Honourable Julia Montague MP (Keeley Hawes), dealing with PTSD at the same time.
Madden said there was a point when he thought he needed to "stop doing this" for a while.
"It weighed very heavy on me. You spend more time in someone else's clothes, saying someone else's words, thinking someone else's thoughts. You do lose a bit of yourself.
"I'm not a method actor in any way, but you get a huge hangover from this. At the end of this, I felt very isolated and broken, much like the character was," he said at The Hollywood Reporter's Drama Actor Rountable.
The actor, who shot to global fame with "Game of Thrones", said he spoke to some soldiers to research for the role, adding it was "tough" to get them to open up.
"... They really don't want to talk about it. People don't want to discuss this at all. (PTSD) is something that people live with everyday. It can be a really trickling level of anxiety you constantly live with, or paranoia, or panic attacks."
Madden added his goal was "to humanise (PTSD) within someone who is in complete denial about it".
The actor was joined by Hugh Grant, Diego Luna, Sam Rockwell, Stephan James and Billy Porter at the roundtable.