The Hunger Games star admits she is ridden with anxiety when she fibs, and puts her fears down to a traumatic childhood moment when her mum caught her being untruthful.
Lawrence made the revelation to a reporter for Vanity Fair during a lunch interview, after she lied to their waitress about enjoying her meal.
She told the journalist, "I'm feeling ill. Look at my leg. I'm shaking my leg because I knew she was going to ask (about the food). I get the weirdest anxiety. I swear to God, I blame my mum.
"When I was in elementary school, I told everyone I had a leg problem and it required a lot of attention, my imaginary leg problem, and I didn't know if I was going to live or die. And my mother comes to school and one of my classmates is like, 'How is Jennifer's leg?' And my mum looks at me and she knows I've been lying and she made me purge.
"I was on the floor and she drew all the lies out of me that I had ever told. She made me tell every single lie, and I was like, crying. It was horrible! I swear, I blame her. Even the smallest thing, like, 'How's your day?' If I'm having a bad day and I say, 'It was good,' I'm like, 'Oh, God!' and I have to purge."