Time Spent on Instagram and Body Image, Self-esteem, and Physical Comparison Among Young Adults in Spain: Observational Study - Alfonso-Fuertes, I.; Alvarez-Mon, M.A.; Sanchez del Hoyo, R.; Ortega, M.A.; Alvarez-Mon, M.; Molina-Ruiz, R.M. (JMIR Formative Research, 2023)