In its ongoing survey of students in Grades 7-12, the Centre for Addiction and Mental Health found that between 1999 and 2011, the percentage of students reporting psychological stress hovered near 34%.
That can include "unhappiness and depression, anxiety, social dysfunction, constant stress or loss of sleep," lead investigator Dr. Robert Mann said in a statement.
But for girls, that kind of suffering is on the rise, up to 43% in 2011 from 36% in 1999.
"Also, girls are reporting distress at a disproportionately high rate compared to 24% of boys who reported these feelings," Mann said.
Girls report both contemplating suicide (14%) and actually attempting to kill themselves (4%) at twice the rate of boys.
Two possible factors behind this are the fact many girls have a negative body image and the prevalence of bullying among girls.
Girls are almost twice as likely as boys to be the victims of cyber-bullying (28%). And 31% of girls report being victimized at school compared to 26% of boys.
"The bullying rates surrounding girls are troubling," said Dr. David Wolfe, director of CAMH's Centre for Prevention Science. "Bullying can have long-term mental health consequences and can affect self-esteem, and hinder the ability to form healthy relationships. The high rates in cyber-bullying are also troubling in that young people today are so technology-driven that bullying now carries over into the home, not just the school setting."
One in five students, or 217,000 kids, reported being the victim of cyber-bullying.
CAMH surveyed 9,288 students in Grades 7 through 12 from 181 schools across the province.