Cyberbullying on social media is linked to depression in teenagers, according to new research that analyzed multiple studies of the on-line phenomenon.

Victimization of young people on-line has received an increasing level of scrutiny, particularly after a series of high-profile suicides of teenagers who were reportedly bullied on various social networks. In 2013, for example, a spate of suicides was linked to the social network Ask.fm, where users can ask each other questions anonymously. The deaths of teens who had been subject to abuse on the site prompted Ask.fm (which was acquired by Ask.com in 2014) to launch new safety efforts. Twitter, likewise, announced plans in April to filter out abusive tweets and suspend bullying users.

Social media use is hugely common among teenagers,

said Michele Hamm, a researcher in pediatrics at the University of Alberta, but the health effects of cyberbullying on social media sites is largely unknown. Regular, face-to-face bullying during the teen years may double the risk of depression in adulthood, and bullying’s effects can be as bad or worse than child abuse, studies show.