Want your teen to stay sane? Keep her off Instagram. According to a new study conducted by the Royal Society for Public Health, the photo- and video-sharing app is the worst for young people's mental health, followed by Snapchat, Facebook, Twitter, and YouTube. Above all other apps, Instagram was found to present the most distorted versions of women's appearances, leading to body-image issues among the platform's users between the ages of 14 and 24. Instagram encourages young women to "compare themselves against unrealistic, largely curated, filtered and Photoshopped versions of reality," the report's author told CNN.