Bullying by text message is more prevalent than physical bullying, a Massey University psychology researcher says.
Jim Sanderson says this form of bullying is a significant contributor to teen suicide.
Mr Sanderson, a former school teacher, studied 210 13 and 14-year-old girls in New Zealand and Canada to determine which personality traits led to text bullying, and found a lack of impulse control is one of the main factors.
Mr Sanderson says the girls' lack of compassion could be due to reality television, which promotes other people's suffering and humiliation as a form of entertainment.
He says girls with low self-esteem tend to dwell on the hurtful messages, which can lead to depression.