Parents of children who suddenly become cranky or withdrawn should take heed - these are signs the child may have fallen victim to a cyberbully.
Psychiatrists and psychologists told My Paper cyberbullying is becoming more prevalent as youth now have easy online access, and many make cyberspace their universe.
Among the cyberbullying cases they have come across here are those involving threats made online.
On Aug 17, a video of a boy spouting a barrage of profanities, which he directed at an unknown person whom he threatened to kill, was posted on the Facebook page of SG Share.
The 11-second video also showed the boy making a rude hand gesture and, at one point, he flashed what appeared to be a knife.
Many netizens mocked the boy's "childish" behaviour in the clip, but parents who watched it expressed concern.
Bank executive Elsie Lee, 37, a mother of two, said: "I worry for the mental health of his victim, and other victims of cyberbullying.
"They might later also develop a fear of interaction."
On the rise of cyberbullying, Dr Adrian Wang, a consultant psychiatrist at Gleneagles Medical Centre, said: "Unfortunately, social media gives bullies a very powerful tool to assert dominance on their victims."
He added that parents may think their kids are safe at home but children can still be reached by bullies online through Twitter, Facebook and Whatsapp.
Dr Carol Balhetchet, director of youth services at the Singapore Children's Society, said online bullies unwittingly, or otherwise, recruit others to add to their vindictive jabs at their victim.
"It often ends up in the situation where there is a whole army of people against just one person," she said.
On what parents can do if their children are subjected to cyberbullying, Dr Wang said: "Parents need to be able to talk to their kids about it, to be accessible and approachable.
"When something is said in the cyber sphere, it is (more) permanent, unlike when said verbally. The effects last much longer."