Johnny Vegas has said his recent ADHD diagnosis "answers a lot of questions" about past behaviours.
The 52-year-old comedian said he had discovered he had attention deficit hyperactivity disorder after a suggestion from presenter Sue Perkins, who shares the same agent.
Adults with ADHD are said to often find it difficult to cope with stress, feel restless and impatient, or have trouble focusing on tasks.
Speaking to BBC Breakfast, the St Helens-born actor said: "A lot of things make sense.
"It's that sense of disorganisation and doing basic tasks. Everybody has an element of it - it's how strong your filter is, I think.
"When you don't have a filter at all, very simple things become very time-consuming. It's like, I'll shift that cup, and then you have 10 other ideas, and you haven't shifted that cup, and then three weeks later that cup's still there and somebody's like, why haven't you shifted that, and it's become this monumental task, and it's built up.
"It's just, I suppose, how your brain organises itself. I always knew I was disorganised... but it [the diagnosis] helps make sense of a lot of things at school. I'm just on the verge of learning about it."
Vegas added the condition "made me who I am" and "that chaos helped me be a better stand-up".
"In some respects you can go back and look at it with regret, but I've had a bit of a charmed life, so it's no regrets," he said.
"I know now, and it helps you make changes, I suppose, as you want to get more responsible later in life. I don't see it as defining me."
Tony Lloyd, the chief executive of the ADHD Foundation, said one in 20 people had ADHD, but that it was "significantly under-identified and under-diagnosed in the UK".
"There are many adults out there who have struggled for years with lots of different sort of characteristics of ADHD, but didn't think they had ADHD because they didn't identify with that enculturated belief that we were all given in school," he said.
"So there are a lot of adults who, now that ADHD is much better understood, are beginning to realise that maybe a lot of the reasons that they've struggled were in fact ADHD."