Keira Knightley insists acting isn't “therapy”.

Keira Knightley needs to have a “really nice time” after filming dark roles.

The Dangerous Method actress doesn’t find acting particularly therapeutic, and admits she needs to properly relax at the end of a day’s work in order to stop her roles making her upset.

“A lot of people say that acting is like therapy, but I don’t go for that,” she said.

“It’s not my cup of tea, it is for some people, but not me. I do, however, find it incredibly cathartic and when you’re playing something so dark you want to have a really nice time afterwards, otherwise it’s far too depressing.”

The 26-year-old actress who is in a relationship with Klaxons rocker James Righton also admitted that her fame has changed her, but she thinks it would be “sad” if she remained the person she was at the beginning of her career.

“Yes, I was different then to the way I am now because you change with your experiences,” she said.

“It would be sad if you didn’t, but my level of fame is not as big as Brad Pitt‘s thankfully.”