The finding marks the first time the centre asked Ontario students about cyber-bullying in 35 years of surveying youth about their mental health and well-being — and one in five students said they were victimized online.
That broke down to 28 per cent of girls surveyed who identified themselves as victims of cyber-bullying, compared to 15 per cent of boys.
The report released Tuesday also found that girls are more likely than boys to be bullied in school.
"What's changed is who's doing it to whom and the girls are reporting more of it than the boys are," said Dr. David Wolfe, a lead researcher on the report who is CAMH's Chair in Children's Mental Health.
"It appears that boys are decreasing it. Maybe they're getting a new message about it, but girls are picking up the slack."
Researchers surveyed 9,288 students from Grades 7 through 12 in 181 schools across Ontario between October and June of last year.
They found that 29 per cent of students in Ontario — estimated at 288,000 adolescents — are affected by bullying. Of that figure, more girls reported being bullied at school and online.
"Girls bully with their social relationships and boys tend to do it more one on one and with more intimidation," said Wolfe, who also teaches at the University of Toronto.
"That's possibly why the cyber-bullying is increasing for girls, because it's easy for them to spread rumours and to do the same things that they were doing before, but even on a bigger scale."
When surveyed about their time spent at school, 31 per cent of girls reported being victimized, compared to 26 per cent of boys.
Those analysing the report said the numbers could shed new light on understanding bullying and measures to combat it.
"I suspect that the anti-bullying programs have been largely focused on boys, because that's what we knew about bullying," said Wolfe.
"But we've forgotten what girls need in this process and they're not totally innocent in this respect either."
Annie Kidder, executive director of the Toronto-based group People for Education, said the results of the report illustrated the differences in bullying between genders.
"I think there is quite a bit of evidence that girls bully differently than boys bully," she said. "Sometimes it's hard for girls to even understand that what they are doing is bullying."
Kidder said there is a need for different approaches to bullying based on highly visible cases in the classroom and less visible incidences online.
"That kind of bullying can even be embarrassing to talk about," she said of cyber-bullying. "That's why it's important to have studies like this and why it's important to have the legislation, because it recognizes all forms of bullying."
The Accepting Schools Act, which passed last month in the Ontario legislature and will come to schools in September, gives school administrators and teachers an opportunity to address not only victims of bullying, but the bullies themselves.
Some of the new policies included establishing a yearly anti-bullying awareness week, hiring special co-ordinators and ensuring that school principals report all incidents to board superintendents.
Dr. Claire Crooks, a clinical psychologist and associate director of the CAMH Centre for Prevention Science, said that it's important to ensure schools are addressing the root of the problem.
"The last several legislative shifts have been all about moving toward a whole school approach," she said.
"People have really stopped thinking about bullying as one specific problem behaviour ... and recognize that we have to have a much more comprehensive approach."
She added that previous legislation ensured schools had a bullying prevention program, but this could simply mean a single assembly or guest speaker, or having students wear certain colours to school to promote bullying prevention.
"The problem is that there's always a gap between what it says on paper and what actually happens in schools," she said.
"The legislation is just paper and what needs to happen is the training and all of these things to actually make it work."
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