She added to Marie Claire magazine: "Between ages 15 and 20, it was really intense. I was constantly anxious. I was kind of a control freak.
"If I didn't know how something was going to turn out, I would make myself ill, or just be locked up or inhibited in a way that was really debilitating."
Meanwhile, Kristen previously revealed why she never smiles for paparazzi photographs.
She shared: "I feel like if I smiled for a paparazzi photo - not that I ever would - that's exactly what people would be desecrating me for.
"They'd be like, 'Now you're going to give it up, now you're a sellout.' Like, OK, what do you want? What would you like?"
- Bang! Showbiz