Sophie Turner says she considered suicide "a lot" when she was younger. The 23-year-old British actress discussed her struggle with depression during Tuesday's episode of the "Phil in the Blanks" podcast with Dr. Phil McGraw. "The biggest challenge -- and I've had it for the longest of all my mental health problems -- is my depression. I've suffered depression for five or six years now," she said. "Learning to love yourself is the biggest challenge, I think." Turner told McGraw she had a happy childhood and didn't experience depression until it hit her "all of a sudden" at age 17 when her friends went away to college and she went through puberty. "I think it was a combination of social media on the rise at that time and also my friends were all going to university and I wasn't going," the star explained. "I was working but I was still living at my parents' house. I felt very alone. And my brothers were away at university as well." "My metabolism was slowing down massively and I was gaining weight," she added. "And then there was the social media scrutiny and everything and that was when it kind of hit me." Turner said she used to be very sensitive to criticism on social media and would believe negative comments about her appearance and abilities. "I'm learning to not be so much now. You see 10 great comments and you ignore them, but one negative comment and it just throws you off," she said. "I used to get a lot of comments about my skin and my weight and how I wasn't a good actress." Turner said her depression manifested as a lack of interest and motivation, as well as suicidal thoughts. "I had no motivation to do anything or go out. Even with my best friends," the actress recalled. "I would just cry and cry and cry over just getting changed and putting on clothes. "It's weird. I say I wasn't very depressed when I was younger, but I used to think about suicide a lot when I was younger," she later shared. "I don't know why though. Maybe it's just a weird fascination I used to have, but yeah, I used to think about it. I don't think I ever would have gone through with it. I don't know." Turner previously discussed her struggle with depression in the April issue of Rolling Stone. She told the magazine therapy and medication have helped her feel "so much better." "Game of Thrones" returned for an eighth and final season on HBO last week. The series co-stars Maisie Williams, Emilia Clarke, Kit Harington and Lena Headey.