Sheridan Smith has revealed she was rushed to hospital and had five seizures after she stopped taking anti-anxiety medication.
Smith said she “went off the deep end” after the 2016 TV Bafta Awards ceremony, where she was nominated for her performance in The C Word.
She was left “humiliated” by jokes made by the host Graham Norton about her “being a drunk”, she said.
She then stopped her medication that night, not realising it was dangerous.
BBC News has asked Norton’s representatives for a comment.
The Cilla and Gavin and Stacey star, made the revelations in a forthcoming ITV special documentary called Sheridan Smith: Becoming Mum, which tells the story of her mental health struggles and her journey to motherhood.
In the film, she recalled: “Graham Norton was hosting and made a joke, basically at my expense, about me being a drunk.
“I was so humiliated, you know, it’s a room full of your peers. And people you want to work with, or have worked with.
“That night, for me, was like the final straw before my brain totally went off the deep end.
“What people didn’t realise is that I’d become addicted to anti-anxiety tablets.”
During the Bafta ceremony, Norton said: “We’re all excited for a couple of drinks tonight. Or, as it’s known in theatrical circles, a few glasses of technical difficulties.”
The comment was a reference to Smith’s departure from a performance of the stage show Funny Girl, which the theatre management said was due to “technical difficulties”. She later pulled out of the show altogether due to mental health issues.
In the ITV documentary, Smith said that after the Baftas she went back to her hotel room and she decided to stop taking the tablets she had been prescribed for her condition.
It was only due to her friend unexpectedly coming to the hotel to see her that she was able to get help.
“It’s a miracle she did (come). It’s like someone was looking out for me because what I didn’t realise is that if you stop these tablets abruptly, you seizure,” said Smith.
“I seizured five times and got rushed to A&E and she’s the one who got me breathing again.”
Smith, who recently had her first child, told the programme that she now feels “calm” and “contentment”.
The actress had an emergency caesarean to deliver her son Billy early this summer, while the country was in lockdown.
During that period she also made one of the short drama films for the ITV’s Isolation Stories series. She played Mel, a heavily pregnant woman who faces having to go through birth without the married father of her child – who’s chosen to stay with his wife and family.
‘Amazing and emotional’
For the new documentary, cameras followed Smith as she attended her first scans, pre-natal classes and sessions with a specialist therapist, as well as at home with fiancé Jamie Horn.
Smith said she wanted to help other women who worry about their mental health issues resurfacing in pregnancy.
“The day he smiled at me was more amazing and emotional even than the day he was born, because you suddenly think, ‘Oh my god – you love me back!’,” she said of her baby.
“Suddenly all those sleepless nights and all that worry goes out the window.”
The documentary also sees the actress explore family issues that she feels could have affected her mental health, including the death of her brother when he was 18 and she was eight, and the death of her father in 2016.
Over the past three years, Smith, who is also an Olivier Award-winning stage actress, has done more TV including BBC One’s The Moorside and ITV’s Cleaning Up.
Last year she made a return to the West End as the narrator in Joseph and the Amazing Technicolor Dreamcoat.
If you need support or help with mental health issues, you can find resources on the BBC Action Line website.