The British star said she was forced to take a year’s hiatus after she felt unable to leave her home due to her newfound celebrity status.
The 33-year-old, who became a household name for her roles in films such as Pirates of the Caribbean, Bend It Like Beckham, and Love Actually, was diagnosed with post-traumatic stress disorder (PTSD), after which she went “deep into therapy”.
Knightley – whose mother, Sharman Macdonald, was born in Glasgow – said that no amount of critical or commercial success could prevent her focusing on negative comments, and said that acting made her feel “worthless”.
In an interview with a US entertainment magazine, she said that while her first prominent roles catapulted her to the A-list, behind the scenes it was difficult to deal with.
She said: “That run of films was completely insane. It’s amazing looking back at it from the outside – you’re like, ‘Woah, that was hit after hit after hit!’ But, from the inside, all you’re hearing is the criticism, really.
“I was aware that I didn’t know what I was doing, you know? I didn’t know my trade, I didn’t know my craft.”
Fame, said Knightley, also made her a target for paparazzi, with up to 20 photographers at a time following her and trying to provoke a reaction.
She said: “It was big money to get pictures of women falling apart, because [consumers] wanted them to be sexy, but you wanted to punish them for that sexuality.
“If you weren’t breaking down in front of them, then it was worth their while to make you break down in front of them. So suddenly there was a level of violence … there was a sense of battle every day leaving the house.”
Knightley, who has been nominated twice for an Academy Award, said that at one point, she did not leave her home for three months.
She also revealed she had to have hypnotherapy to prevent a panic attack in order to be able to attend the Bafta Awards in 2008, when she was nominated for Atonement.
After returning to work, Knightley said that she had a new-found perspective on acting, and “didn’t care” about criticism.
Nowadays, she added, she feels like she in “in a good place where I feel pretty confident about what I can do”.
The actor, from Richmond, London, is the latest high-profile figure to speak out about their experience of PTSD.
The US singer Ariana Grande revealed she was diagnosed with PTSD following the bomb attack at the end of her Manchester Arena concert in 2017.
Pop star Lily Allen has also told of how she suffered from the disorder after her son was stillborn in 2010.