Keira Knightley has revealed she had a mental breakdown at 22 and was diagnosed with post-traumatic stress disorder (PTSD) as she struggled with her sudden rise to fame.
The actress said she was forced to take a year off after starring in Pirates of the Caribbean and Love Actually.
Despite her success she admitted criticism of her acting made her feel "worthless".
And she said she was too scared to leave the house and face the paparazzi.
Knightley's fame rose sharply after she starred in Bend it Like Beckham, Pirates of the Caribbean and Love Actually.
She told the Hollywood Reporter Awards Chatter podcast looking back 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."
She said her lack of acting training made her focus on the negative.
"I literally felt like I was worthless," she admitted.
That continued even after getting a best actress Oscar nomination for her performance in Pride and Prejudice in 2005.
"I felt pretty much like actually I didn't exist and I was this weird creature with this weird face that people seemed to respond to in quite an extreme way, and I couldn't quite figure any of it out."
- Post-traumatic stress disorder (PTSD) is an anxiety disorder caused by very stressful, frightening or distressing events.
- Someone with PTSD often relives the traumatic event through nightmares and flashbacks, and may experience feelings of isolation, irritability and guilt.
- They may also have problems sleeping, such as insomnia, and find concentrating difficult.
- These symptoms are often severe and persistent enough to have a significant impact on the person's day-to-day life.
She said being followed by paparazzi made leaving the house "a sense of battle" every day.
Up to 20 photographers at a time would follow her and bait her for a reaction.
"If you [female stars] 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, it felt, in the air. That is not a thing that anybody would react to well."
At one point Knightley did not leave the house for three months. She also had to have hypnotherapy to prevent a panic attack in order to be able to attend the Baftas in 2008, where she was nominated for Atonement.
In her year off she said she went "deep into therapy". On returning to work in 2010, she "felt really good" and suddenly did not care about the views of others.
Knightley is the latest celebrity to talk about their experience of PTSD.
Ariana Grande revealed she had post-traumatic stress disorder following the bombing at her Manchester concert.
Lily Allen revealed she suffered from the disorder after the stillbirth of her son in 2010.
Will Young also spoke about how he developed PTSD from a culmination of years of hiding his homosexuality, being bullied at primary school and being separated from his twin brother at birth.
In August this year Mel B entered rehab for treatment for PTSD following her divorce and the death of her father.
"If I can shine a light on the issue of pain, PTSD and the things men and women do to mask it, I will do," the Spice Girl said.