(CNN) -- Roughly 20% of high school students report being bullied at school in the past year, according to the Centers for Disease Control and Prevention, and 15% of high school students said they were bullied online.
That number has gone down significantly since the federal government started collecting data on the problem in 2005. A decade ago, 28% of students reported being bullied.
Why? One reason is that anti-bullying laws seem to actually work. That's what a new study in JAMA Pediatrics suggests, although not all bullying laws are equally impactful.
Bullying behavior is typically defined as a persistent pattern of harassment and intimidation that's directed at an individual and can be physical or verbal.
Bullying behavior is meant to scare, isolate and humiliate the victim. It can come in the form of threats, spreading rumors, attacks or purposeful exclusion of the victim. Bullying can create deep emotional scars for victims and for bystanders who witness this behavior. The impact can be felt for a lifetime, and it leaves people depressed, anxious and can even lead to suicide.
Anti-bullying laws address an old problem
In the wake of several high-profile suicides among students who were chronically bullied, and after two students who said they were constantly bullied attacked their fellow students in 1999 at Columbine High School in Colorado, various states started passing laws to stop bullying behavior among students. Every state in the country now has something on the books.
"It's hard to believe 15 years ago we didn't really have anti-bullying laws," said lead author Dr. Mark Hatzenbuehler.
Hatzenbuehler is an association professor in the department of sociomedical sciences at Columbia University. What makes the study important is that it's the first to look for a direct effect of these laws on students.
What's striking about the study's findings, Hatzenbuehler said, is exactly how much of an effect these laws have had to stop bullying.
The laws, he said, have helped everyone, even segments of the population that are typically seen as more at risk: the obese or overweight, people with disabilities and people who identify as lesbian, gay, bisexual or transgender.
Looking at data from more than 60,000 high school students in public and private schools in 25 states, the study found that states that did have anti-bullying laws with at least one Department of Education recommendation saw fewer instances of bullying.
In 2010, the U.S. Department of Education created a document that laid out 11 recommendations for effective bullying laws. They included spelling out what is prohibited behavior, training in bullying prevention and monitoring to make sure the policies are enforced.
This study found that the states with laws that had even one of these Department of Education suggestions showed 24% less reports of in-person bullying and 20% less reported cyberbullying.
Students in Alabama, for instance, saw a decline in bullying that was so significant only 14% reported a problem; whereas in South Dakota 27% of students reported being the victim of bullying. Across the 25 states studied (there was not enough data on the other states), the average rate of bullying matched the CDC figures at around 20%.
That still leaves millions of U.S. children face regular harassment and don't feel safe when they go to class.
While more work needs to be done to fully understand the combination of law that works best -- the study was observational and did not get at why these laws were effective -- what does seem to consistently work is when states define what bullying behavior is prohibited, and it helps when the law requires schools to create and enforce anti-bullying policies.
The authors theorize laws that are specific about what constitutes bullying may empower school administrations to stop the behavior. Earlier studies have shown that programs that have the most impact also teach parents and teachers that bullying should not be the norm, and encourage peers and adults to intervene to stop the behavior.
In the future, Hatzenbuehler hopes to expand the study to include younger children. Middle schoolers do tend to face a disproportionate amount of bullying compared with other age groups, according to earlier studies. But Hatzenbuehler thinks his study effectively shows that bullying doesn't have to be business as usual among children.
"Laws actually work, and as we get a better understanding of what combination of law works best we can create a gold standard of legislation," that will be even more impactful, Hatzenbeuhler said.
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