Paddy Considine says his Asperger's diagnosis was a positive life-changer.
The 45-year-old actor was told he had the developmental disorder in his mid-30s, and he found the diagnosis "incredibly helpful" because he could start to understand and identify his behaviour.
The "Informer" star said: "The period before I got my diagnosis during my mid-30s was the lowest of my life.
"I was having social problems and they were getting worse. I was finding small, day-to-day interactions very difficult.
"I can find walking the kids to school and saying good morning to people harder than standing on stage in front of 1,000 people on Broadway.
"The diagnosis was, for me, incredibly helpful. It meant I could identify it. I could call it something."
While Paddy suffers from social problems, he has long had an interest in drama and has been unintentionally impersonating people since a young age as a "defence mechanism".
The "Bourne Ultimatum" star said: "I always imitated people from a young age.
"Not just little impressions - I'd subconsciously imitate them for months, sometimes years.
"As a kid, I'd be Rick from "The Young Ones" constantly; at college, I was Alan Partridge. But I didn't even know I was doing it.
"I think it's a defence mechanism."
The "Death of Stalin" actor always felt "different" from his family, and he wanted to make something of himself so people wouldn't automatically assume he was a "menace" because of his surname.
Speaking to The Times Magazine, he added: "People would still react to me like I was some sort of menace because I was a Considine.
"It wasn't like I wanted to act because I loved drama - I just wanted to be seen as something other than the kid off the estate, I wanted to be seen in a different light."