Among the 1041 students who had no signs of anxiety and depression at the outset, those who reported “unhealthy” Internet use were two and a half times as likely to have symptoms of depression at the second evaluation.

“This result suggests that young people who are initially free of mental health problems but use the Internet pathologically could develop depression as a consequence,” Lawrence T. Lam, of the University of Notre Dame Australia in Darlinghurst, and Zi-Wen Peng, of SunYat-Sen University in Guangzhou, write in the Archives of Pediatrics and Adolescent Medicine.