Kim Cattrall has opened up about her battle with chronic insomnia, saying it became "a tsunami" in her life.
The Sex And The City star's struggle with sleeplessness led to her pulling out of a West End production of Penelope Skinner's play Linda in 2015.
She told the Radio Times of her condition: "It was a gorilla sitting on my chest. I didn't understand the debilitating consequence of having no sleep. It becomes a tsunami. I was in a void."
Kim said she didn't want to disappoint the audience, the theatre or her co-stars, but believed leaving the show was crucial to her mental health.
"Letting go of all that was the hardest part but I realised the work that I really needed to do was more important than the play - it was work on my sanity," she said.
Asked if her sanity had been at risk, she said: "Coming back to the US, I hadn't slept for 48 hours and had to wait six hours to get my 18-year-old cat through customs.
"When the customs officer said, 'So, how much is your cat worth?' I couldn't stop laughing hysterically."
The actress, 59, left the production at the Royal Court Theatre in London during rehearsals and she was replaced by Noma Dumezweni.
Kim faced criticism for pulling out but said she was not interested in listening to that "noise".
"I have my own voice on social media, where I can say: if you're interested in what really happened, the whole story is more complex than being a disease of the week, than someone saying, 'I have this battle'," she said.
The Liverpool-born actress returned to New York and turned to cognitive behavioural therapy to help her tackle her insomnia.
"So last Christmas wasn't about friends and relations; it was a monastic experience of trying to delve," she said.
This week's Radio Times is on sale from Tuesday.