By Lisa Rapaport

NEW YORK (Reuters Health) - Anti-bullying policies in most U.S. states aim to protect kids against abuse from their peers in school and online, but their effectiveness varies widely depending on where students live, a study suggests.

Researchers analyzed survey data on bullying from almost 62,000 students in grades 9 through 12 to see how their experiences varied based on the type of laws in their home state.

In states where the laws followed at least one U.S. Department of Education (DoE) recommendation for anti-bullying policies, teens were 24% less likely to report bullying and 20% less likely to report cyber-bullying, researchers found.

The DoE recommends, for example, that laws include explicit descriptions of prohibited behaviors and spell out clear reporting practices and specific consequences.

"Although anti-bullying policies by themselves can't eradicate bullying, these results suggest that such policies are an important part of a comprehensive strategy for preventing bullying among youth," said lead author Dr. Mark Hatzenbuehler, a public health researcher at Columbia University in New York.

Bullying is one of the most common forms of peer aggression in schools, and both perpetrators and victims may experience mental health problems linked to this behavior such as anxiety, depression or social isolation, Dr. Hatzenbuehler and colleagues noted in an article online October 5 in JAMA Pediatrics.

Researchers examined student survey responses about bullying in 25 states and DoE assessments of anti-bullying policies in those states for 2011.

Bullying rates ranged from about 14% in Alabama to almost 27% in South Dakota, with an average rate of 20% across all the states in the study.

Rates of cyber-bullying ranged from roughly 12% in Alabama to nearly 20% in South Dakota, with an average of about 16%.

The researchers also assessed the effectiveness of 16 components of anti-bullying legislation recommended by DoE. The components most strongly tied to lower rates of bullying and cyber-bullying included defining these behaviors and spelling out consequences.

Only states with laws passed prior to the survey on bullying were included in the analysis, and more research is needed to assess the effectiveness of anti-bullying legislation in all 50 states, the authors note.

Even so, previous research points to some steps schools can take to curb this behavior, Dr. Lisa Jones, with the Crimes Against Children Research Center at the University of New Hampshire in Durham, told Reuters Health by email.

"Research suggests that a combination of positive school climate, trust between students and staff, clear and consistent victimization response policies, and evidence-based prevention education programs for youth can make a difference - so these are the directions schools should be heading," Dr. Jones, who wasn't involved in the study, said.

The most effective policies to prevent bullying will also look beyond just schools to include parents, coaches, and other adults who are regularly involved with children, Dr. Megan Moreno, a specialist in adolescent health at Seattle Children's Research Institute, told Reuters Health by email.

"Bullying commonly takes place in schools, but also takes place on sports teams, in Girl Scout troops, at summer camps, and within almost every youth-oriented activity," said Dr. Moreno, who wasn't involved in the study.

Policing behavior that takes place online requires additional vigilance, Dr. Matthew Davis, a pediatrician at the University of Michigan in Ann Arbor and director of the C.S. Mott Children's Hospital National Poll on Children's Health, told Reuters Health by email.

"One of the best ways for parents to keep kids safe from cyber-bullying is to make sure that kids know that they should tell their parents if they see something or read something online that makes them upset," said Dr. Davis, who wasn't involved in the study.

The Center for Injury Epidemiology and Prevention at Columbia University and the University of Iowa Injury Prevention Research Center partially supported this research.