Kim Cattrall pulled out of a play because of a "tsunami" of insomnia.
The 'Sex and the City' actress had been due to play the title role in 'Linda' at London's Royal Court Theatre last year but withdrew two weeks before the production opened for the sake of her "sanity" after seeking medical advice.
The 59-year-old actress hadn't slept for 48 hours when she returned to the US from the UK and described her insomnia as a "gorilla sitting on my chest".
She told Radio Times magazine: "I didn't understand the debilitating consequence of having no sleep. It becomes a tsunami. I was in a void.
"I didn't want to let down the audience, the theatre, playwright or the actors.
"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 or my sanity."
Kim - who was replaced in the production by Noma Dumezweni - didn't listen to the "noise" of social media criticism when she pulled out of the play because she knew her problem was more "complex" than people realised.
She said: "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 disease of the week', than someone saying, 'I have this battle'.
"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 'Sensitive Skin' actress turned to cognitive behavioural therapy to combat her chronic sleeplessness.
She said: "It's like putting on a pair of sneakers and going into your past to get a new perspective. And I was gentle with myself. So last Christmas wasn't about friends and relations; it was a monastic experience of trying to delve."
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