While deaths are the most severe consequences of interpersonal violence, the effects of school violence include: interference with the normal learning activities of students; weapon carrying for defensive purposes on school grounds; serious injury and attendant medical costs and absenteeism from school [6-8]. The Centers for Disease Control and Prevention (CDC) have reported that adolescents who felt unsafe at school were likely to be absent [9].

A three-stage cluster sample design was used to obtain a nationally representative sample of students in grades 9–12. In the first-stage of sampling, 1,261 primary sampling units (PSUs), consisting of counties, subareas of large counties, or groups of smaller, adjacent counties were obtained. The 1,261 PSUs were categorized into 16 strata according to their metropolitan statistical area (MSA) status. From these 1,261 PSUs, 57 were selected with probability proportional to overall school enrollment size for the PSU. In the second stage of sampling, a total of 203 schools with any of grades 9–12 were selected with probability proportional to school enrollment size. The third stage of sampling consisted of randomly selecting, in each chosen school and in each of grades 9–12, one or two classrooms from either a required subject or a required period (e.g., homeroom or second period).

All students in selected classes were eligible to participate. There was no replacement of schools, classes, or students that refused to participate. Black and Hispanic students were oversampled in order to allow for stratified analysis of these groups. The sampling of these groups provided that: 1) larger sampling rates were used to select PSUs that are in high-black and high-Hispanic strata; 2) a modified measure of size was used that increased the probability of selecting schools with a disproportionately high minority enrollment; and 3) two classes per grade, rather than one, were selected in schools with a high minority enrollment. A weight based on student sex, race/ethnicity, and grade level was applied to each record to adjust for school and student non-response and oversampling of black and Hispanic students. The overall weights were scaled so that the weighted count of students equals the total sample size, and the weighted proportions of students in each grade match the national population proportions. For the 2005 national YRBS, 13,953 questionnaires were completed in 159 schools. The school response rate was 78%, and the student response rate was 86%. The school response rate multiplied by the student response rate produced an overall response rate of 67%. CDC's Institutional Review Board granted clearance for the national YRBS.

Table ​Table22 shows the results for factors associated with physical fighting. All the results were similar for both sexes except for the factors: Ethnicity (American Indian or Alaska Native, and Native Hawaii or other Pacific Islander), and watching videogames. In order to adjust among other factors for sex, a multivariate analysis was conducted. The results are shown in Table ​Table3.3. Respondents aged 17 years or older were less likely to report physical fighting than those who were 14 years or younger (OR = 0.43; 95% CI [0.31, 0.59] for 17 years old and OR = 0.41; 95% CI [0.29, 0.59] for 18 years olds or older). Compared to Whites, American Indian or Alaska Native, Natives, Blacks, Native Hawaii or other Pacific Islanders, and Hispanics were more likely to report physical fighting on school property (OR = 2.11; 95% CI [1.22, 3.66], OR = 1.72; 95% CI [1.42, 2.09], OR = 2.18; 95% CI [1.01, 4.79], and OR = 1.74; 95% CI [1.41, 2.16] respectively). Physical fighting on school property was also positively associated with cigarette smoking (OR = 1.70; 95% CI [1.37, 2.10]), drinking alcohol (OR = 1.45; 95% CI [1.20, 1.76]), use of illegal drugs (OR = 1.73; 95% CI [1.42, 2.12]), having had property stolen or deliberately damaged on school property (OR = 2.06; 95% CI [1.74, 2.44]), having been threatened or injured with a weapon on school property (OR = 2.63; 95% CI [2.06, 3.34]), and playing videogame three or more hours a day (OR = 1.29; 95% CI [1.07, 1.56]).

In both bivariate and multivariate analysis the following were positively associated with having engaged in a physical fight on school property: male gender; non-white race (except Asians); substance use (alcohol, cigarette, and illicit drugs); having had property stolen or damaged; having ever been threatened or injured with weapon and exposure to video games.

The higher male prevalence compared to females is perhaps not surprising. Males top females in almost all unhealthy behaviors such as homicides, alcohol, cigarette smoking, not presenting for health care when ill and having multiple and concurrent sex partners [16-21]. Cultural perceptions of masculinity are likely to be the reasons that males predominate in many unhealthy behaviors [22,23]. Society is likely to be tolerant to male violence behaviors than it is to female violent behaviors. As male adolescents may feel violence among males is acceptable, there may be no strong disincentives to prevent them from violent behaviors.

We have observed the race-ethnicity differences that are associated with physical fighting among high school students in this study. Compared to Whites, American Indian or Alaska Native, Blacks and Hispanics were more likely to report physical fighting while Asians were less likely to engage in physical fighting. We do not believe these differences are due to any genetic differences but rather as a result of different socio-economic environments that adolescents live in. Previous studies have reported that with the exception of Asians, members of all other ethnic minority groups were more socioeconomically disadvantaged than White and that low socioeconomic status (SES) was a determinant of poor health outcomes [24-26]. Racial difference in health indices such as cardiovascular, perinatal and breast cancer mortality have consistently been observed [27-29], largely as a result of differences in access to health care. Furthermore almost always, with regarding to violence and incarcerations, Blacks and Hispanics are more likely to experience these than white. Ethnic minority youth live in unsafe environments, and so are exposed to violence and crime more than whites. As a result of this influence, they are also likely to engage in violent behaviors.

Adolescents who reported having had property damaged or stolen at school and those who reported having been threatened or injured with a weapon were more likely to have engaged in a fight. This may suggest that previous victimization may trigger adolescents to engage in a fight rather than solve interpersonal differences in a different way. Rudatsikira et al have reported that weapon carrying by California adolescents was associated with previous victimization [30]. These authors suggested that adolescents might have carried weapons in self-defense for any potential victimization. Glew et al have reported that victims of bullying in a school district in the United States felt it was "not wrong" to carry weapons to schools [31]. Among this group of 5391 school adolescents, 26% had been involved in bullying either as victims or as perpetrators.

We found that adolescents less than 14 years were more likely to report having engaged in a fight than older study participants. We believe this may be due to the fact that younger adolescents may not have gotten non-violent conflict resolution skills compared to older adolescents. Furthermore, younger adolescents are less likely to severely injured others such that the consequences of their actions attract parental or school authorities attention. Finally, parents are likely to neglect young adolescents fighting than if fighting occurs among older adolescents. All these reasons may discourage fighting among older adolescents while younger adolescents may not have as much disincentive. Johnson et al [32] have reported a qualitative study in which via focus group discussions, youth reported that fighting may be a necessary outcome of a disagreement. Although it would obviously be desirable that no physical fighting occurred, the youths interviewed suggested that physical fighting had potential to prevent more serious violence.

The association between self reported history of having 3 or more hours of video-game play and physical fighting is interesting. Ez-Elarab et al [33] have reported that elementary school children who had preference of violent video games were more likely to exhibit violent behaviors than those who did not have that preference. Previous reports have suggested that short-term effects of exposure to media violence are mostly due to the following: i) priming processes, ii) arousal processes, and ii) immediate mimicking of specific behaviors [34-36]. In brief, the priming process is when watching violent media makes the individual to associate similar situation seen in the video but now in real life to violence. Arousal is the process where having viewed violent media makes one excited and may engage in violence when provoked. Mimicry occurs when imitation occurs as part of observational learning [37-39].

The association between the numbers of hours adolescents play video games and having been engaged in a physical fight may also be just a marker of unsupervised time that the adolescent has at his or her disposal. Adolescents who are alone at home or elsewhere may be more likely to play video games than those that are supervised. Unsupervised adolescents are more likely to engage in a diversity of anti-social and unhealthy life styles such as sexual intercourse, cigarette smoking, violence and illicit drug use [40-43].

ASM participated in the interpretation of the results and drafting of the manuscript.

SS participated in the interpretation of the results and drafting of the manuscript.