A study of more than 13,500 high school students in the US has found that exercising four times a week is associated with a 23 percent reduction in suicide attempts and suicidal thoughts among students who have been bullied.

Almost one in five students in the study reported experiencing bullying at school, and research has shown that these teenagers will be at a higher risk of suicide, as well as mental health issues such as anxiety and depression, and declining academic performance. But this is the first study to suggest that exercise might help with those factors.

"I was surprised that it was that significant and that positive effects of exercise extended to kids actually trying to harm themselves," lead researcher Jeremy Sibold, a movement scientist at the University of Vermont, said in a press release. "Even if one kid is protected because we got them involved in an after-school activity or in a physical education program it's worth it."

The data were taken from the US Centre for Disease Control's National Youth Risk Behaviour Survey, and it showed that 30 percent of high school students reported feeling sad for two or more weeks in the past year. More than 22 percent had thought about suicide, and 8.2 percent had tried to kill themselves during the same time period.

Those numbers on their own are pretty shocking, but the study also found that bullied students are twice as likely to report feeling sad, and three times more likely to think about or attempt suicide than their peers who aren't picked on.

But the good news is that those who exercised four or more days per week were significantly less likely to feel sad for long periods of time, have suicidal thoughts, or attempt suicide. After controlling for other factors that could be involved, such as age, gender, and race, the researchers found that regular exercise was linked to a 23 percent reduction in suicide attempts and suicidal thoughts in bullied students.

To be clear, the study only found a correlation between exercise and mental health in bullied students, and didn't show that exercise directly reduced the number of suicidal thoughts or attempts. That may or may not be the case, but the study simply looked at the trends, so it can't provide those answers. But the link suggests that physical activity could be worth looking into further as a potential way to help bullied children cope.

"Considering the often catastrophic and long lasting consequences of bullying in school-aged children, novel, accessible interventions for victims of such conduct are sorely needed," the researchers write in The Journal of the American Academy of Child and Adolescent Psychiatry. The results "potentially [implicate physical activity] as a salient option in response to bullying in schools", they add.

Unfortunately, the study comes at a time when schools in the US are cutting the amount of time kids spend being active each week, and around the world young people are becoming increasingly sedentary. The researchers hope their work may encourage families to be more active.

"It's scary and frustrating that exercise isn't more ubiquitous and that we don't encourage it more in schools," said Sibold. "Instead, some kids are put on medication and told 'good luck.' If exercise reduces sadness, suicide ideation, and suicide attempts, then why in the world are we cutting physical education programs and making it harder for students to make athletic teams at such a critical age?"