Introduction to Risk and Protective Factors

The concepts of risk and protection are integral to public health. A risk factor is anything that increases the probability that a person will suffer harm. A protective factor is something that decreases the potential harmful effect of a risk factor. In the context of this report, risk factors increase the probability that a young person will become violent, while protective factors buffer the young person against those risks. The public health approach to youth violence involves identifying risk and protective factors, determining how they work, making the public aware of these findings, and designing programs to prevent or stop the violence.

Risk factors for violence are not static. Their predictive value changes depending on when they occur in a young person's development, in what social context, and under what circumstances. Risk factors may be found in the individual, the environment, or the individual's ability to respond to the demands or requirements of the environment. Some factors come into play during childhood or even earlier, whereas others do not appear until adolescence. Some involve the family, others the neighborhood, the school, or the peer group. Some become less important as a person matures, while others persist throughout the life span. To complicate the picture even further, some factors may constitute risks during one stage of development but not another. Finally, the factors that predict the onset of violence are not necessarily the same as those that predict the continuation or cessation of violence.

Violence prevention and intervention efforts hinge on identifying risk and protective factors and determining when in the course of development they emerge. To be effective, such efforts must be appropriate to a youth's stage of development. A program that is effective in childhood may be ineffective in adolescence and vice versa. Moreover, the risk and protective factors targeted by violence prevention programs may be different from those targeted by intervention programs, which are designed to prevent the reoccurrence of violence.

This report groups risk and protective factors into five domains: individual, family, peer group, school, and community, which includes both the neighborhood and the larger society (Box 4-1). Factors do not always fit neatly into these areas, however. Broken homes are classified as a family risk factor, but the presence of many such families in a community can contribute to social disorganization, an important community-level risk factor (Bursik & Grasmick, 1993; Elliott et al., 1996; Sampson & Lauritsen, 1994).

Table

Box 4-1. Early and late risk factors for violence at age 15 to 18 and proposed protective factors, by domain.

Risk Factors

Risk factors are not necessarily causes. Researchers identify risk factors for youth violence by tracking the development of children and adolescents over the first two decades of life and measuring how frequently particular personal characteristics and social conditions at a given age are linked to violence at later stages of the life course. Evidence for these characteristics and social conditions must go beyond simple empirical relationships, however. To be considered risk factors, they must have both a theoretical rationale and a demonstrated ability to predict violence -- essential conditions for a causal relationship (Earls, 1994; Kraemer et al., 1997; Thornberry, 1998). The reason risk factors are not considered causes is that, in most cases, scientists lack experimental evidence that changing a risk factor produces changes in the onset or rate of violence.

As used in this report, risk factors are personal characteristics or environmental conditions that predict the onset, continuity, or escalation of violence.

The question of causality has practical implications for prevention efforts. Prevention depends largely on risk factors being true causes of violence. In practical terms, research has amassed enough strong, consistent evidence for the risk factors discussed in this report to provide a basis for prevention programs, even though a strict cause-and-effect relationship has been established for relatively few of them.

Most of the risk factors identified do not appear to have a strong biological basis. Instead, it is theorized, they result from social learning or the combination of social learning and biological processes. This means that violent youths who have violent parents are far more likely to have modeled their behavior on their parents' behavior -- to have learned violent behavior from them -- than simply to have inherited it from them. Likewise, society's differing expectations of boys and girls -- expecting boys to be more aggressive, for example -- can result in learned behaviors that increase or decrease the risk of violence.

The bulk of the research that has been done on risk factors identifies and measures their predictive value separately, without taking into account the influence of other risk factors. More important than any individual factor, however, is the accumulation of risk factors. Risk factors usually exist in clusters, not in isolation. Children who are abused or neglected, for example, tend to be in poor families with single parents living in disadvantaged neighborhoods beset with violence, drug use, and crime. Studies of multiple risk factors have found that they have independent, additive effects -- that is, the more risk factors a child is exposed to, the greater the likelihood that he or she will become violent. One study, for example, has found that a 10-year-old exposed to 6 or more risk factors is 10 times as likely to be violent by age 18 as a 10-year-old exposed to only one factor (Herrenkohl et al., 2000).

Researchers have theorized that risk factors also interact with each other, but to date they have found little evidence of interaction. What evidence does exist suggests that interactions between or among factors produce only small effects, but work in this area is continuing. To date, much more research has been done on risk factors than protective factors, but that picture, too, is changing.

Developmental Progression to Violence

Scientific theory and research take two different approaches to how youth violence develops -- one that focuses on the onset of violent behavior and its frequency, patterns, and continuity over the life course and one that focuses on the emergence of risk factors at different stages of the life course. Chapter 3 describes two developmental trajectories for the onset of violent behavior -- one in which violence begins in childhood (before puberty) and continues into adolescence, and one in which violence begins in adolescence.

In contrast, this chapter considers the timing of risk factors. It identifies the individual characteristics, experiences, and environmental conditions in childhood or adolescence that predict involvement in violent behavior in late adolescence -- that is, age 15 to 18, the peak years of offending. Research shows that different risk factors may emerge in these two developmental periods and that the same risk factors may have different effect sizes, or predictive power, in these periods.

The timing of risk factors and the onset of violence are connected. Only risk factors that emerge in early childhood can logically account for violence that begins before puberty. However, these early risk factors may or may not be implicated in violence that begins in adolescence. In fact, studies show that many youths with late-onset violence did not encounter the childhood risk factors responsible for early-onset violence. For these youths, risk factors for violence emerged in adolescence (Huizinga et al., 1995; Moffitt et al., 1996; Patterson & Yoerger, 1997; Simons et al., 1994).

Table 4-1 lists early and late risk factors and estimates their effect sizes for violence at age 15 to 18. It does not distinguish between youths who became violent before puberty and those who first became violent in adolescence; both groups are included among youths who were violent in late adolescence. However, the table does indicate that different risk factors emerge before puberty (age 6 to 11) and after puberty (age 12 to 14) and that the same risk factors have different effect sizes in these periods. Thus, for example, the table shows that substance use in childhood has a greater effect on violence at age 15 to 18 than parental abuse or neglect does and that substance use in childhood has a greater effect on violence than substance use in early adolescence. (The table is discussed at greater length below, in A Note on Sources.)

Table

Table 4-1. Effect sizes of early and late risk factors for violence* at age 15 to 18.

The distinction between early and late risk factors is important. To be effective, prevention programs must address the risk factors that appear at a particular stage of development. The observed clustering of risk factors in childhood and in adolescence provides clear targets for intervention during these stages of the life course.

Limitations of Risk Factors

Risk factors are powerful tools for identifying and locating populations and individuals with a high potential for becoming violent, and they provide valuable targets for programs aimed at preventing or reducing violence. But there are important limitations to our knowledge about and use of risk factors.

The following cautions are worth bearing in mind:

• No single risk factor or set of risk factors is powerful enough to predict with certainty that youths will become violent. Poor performance in school is a risk factor, for example, but by no means will all young people who perform poorly in school become violent. Similarly, many youths are exposed to multiple risks yet avoid becoming involved in violence (Garmezy, 1985; Rutter, 1985; Werner & Smith, 1982, 1992).
• Because public health research is based on observations and statistical probabilities in large populations, risk factors can be used to predict violence in groups with particular characteristics or environmental conditions but not in individuals.
• Given these two limitations, assessments designed to target individual youths for intervention programs must be used with great care. Most individual youths identified by existing risk factors for violence, even youths facing accumulated risks, never become violent (Farrington, 1997; Huizinga et al., 1995; Lipsey & Derzon, 1998).
• Some risk factors are not amenable to change and therefore are not good targets for intervention (Earls, 1994; Hawkins et al., 1998a). Being born male is an example.
• Of the risk factors that are amenable to change, some are not realistic targets of preventive efforts. Eliminating poverty is not a realistic short-term goal, for example, but programs that counter some of the effects of poverty are. (Eliminating or reducing poverty should be a high-priority long-term goal, however.)
• Some situations and conditions that influence the likelihood of violence or the form it takes may not be identified by longitudinal studies as risk factors (predictors) for violence. Situational factors such as bullying, taunting, and demeaning interactions can serve as catalysts for unplanned violence. The social context can influence the seriousness or form of violence -- for example, the presence of a gun or a gathering crowd of peers that makes a youth feel he (or she) needs to protect his (or her) reputation. These may not be primary causes of violence, yet they are contributing factors and are important to understanding how a violent exchange unfolds. Such influences, although important, may not be identified in this report because of the way risk factors are defined.
• Many studies of risk factors, particularly earlier ones, drew their samples from white boys and young men. The limited focus of these studies calls into question their predictive power for girls and women and for other racial or ethnic groups. Differences among cultures and their socialization and expectations of girls and boys may modify the influences of some risk factors in these groups.

Nonetheless, most of the risk factors identified in this report do apply broadly to all young people. All children go through the same basic stages of human development -- and prevention of youth violence is based on understanding when and how risk factors come into play at various stages of development. Moreover, there is some evidence that most risk factors are equally valid predictors of delinquency and violence regardless of sex, race, or ethnicity (Rosay et al., 2000; Williams et al., 1999). Sophisticated studies that identify how cultural differences affect the interplay of the individual and his or her surroundings will make possible more effective prevention efforts.

Risk Factors in Childhood

The first decade of life encompasses a vast period of human development. Infants form attachments to parents or other loving adults and begin to become aware of themselves as separate beings. As toddlers, they begin to talk, to assert themselves, to explore the world around them, and to extend their emotional and social bonds to people other than their parents.

The start of school is a milestone in children's continuing social and intellectual development. Other children become more important in their lives, though still not as important as family members. They begin to empathize with others and hone their sense of right and wrong. As they progress through elementary school, children gain valuable reasoning and problem-solving skills as well as social skills.

Exposure to or involvement in violence can disrupt normal development of both children and adolescents, with profound effects on their mental, physical, and emotional health. ⁴ In addition, exposure to violence affects children and adolescents differently at different stages of development (Marans & Adelman, 1997).

Young children exposed to violence may have nightmares or be afraid to go to sleep, fear being left alone, or regress to earlier behavior, such as baby talk or bed-wetting. They may exhibit excessive irritability or excitability. Violence in the family, especially, may inhibit young children's ability to form trusting relationships and develop independence.

Elementary school children who live in violent neighborhoods may also experience sleep disturbances and be less likely to explore their environment. In addition, they can become frightened, anxious, depressed, and aggressive. They may have trouble concentrating in school. Because they understand that violence is intentional, they may worry about what they could have done to prevent or stop it (Osofsky, 1999).

Violence also affects parents. Adults living in violent households or neighborhoods may not be able to keep their children safe or to protect them from harmful influences. Some parents living in unsafe neighborhoods do not let their children play outside. While this solution may safeguard children temporarily, it can also impede healthy development. Parents in these situations understandably feel helpless and hopeless. Those who have been traumatized by violence themselves may, like their children, become anxious, withdrawn, or depressed. Under such circumstances, parents cannot respond spontaneously and joyously to their children, making it difficult for children to develop strong, secure attachments to their parents. Forming a bond with a loving, responsive parent or other adult caregiver is an essential factor in healthy development (Furstenberg et al., 1999; Osofsky, 1999; Patterson & Yoerger, 1997). Children and families exposed to or involved in violence may want to seek professional advice in addressing their mental, physical, and emotional health concerns.

Risk Factors in Adolescence

Violence increases dramatically in the second decade of life, peaking during late adolescence at 12 to 20 percent of all young people and dropping off again sharply by the early twenties. Some of these youths followed the childhood-onset trajectory, becoming violent before puberty and escalating their rate of offending during adolescence. But over half of all violent youths begin their violent behavior in mid- to late adolescence. These youths gave little indication of problem behavior in childhood and did not have poor relations with their parents.

There are numerous theories about why violence begins in adolescence, but a few themes run through most of them (Elliott & Tolan, 1999; Pepler & Slaby, 1994). Developmentally, puberty is accompanied by major physical and emotional changes that alter a young person's relationships and patterns of interaction with others. The transition into adolescence begins the move toward independence from parents and the need to establish one's own values, personal and sexual identity, and the skills and competencies needed to compete in adult society. Independence requires young people to renegotiate family rules and degree of supervision by parents, a process that can generate conflict and withdrawal from parents. At the same time, social networks expand, and relationships with peers and adults in new social contexts equal or exceed in importance the relationships with parents. The criteria for success and acceptance among peers and adults change.

Adapting to all of these changes in relationships, social contexts, status, and performance criteria can generate great stress, feelings of rejection, and anger at perceived or real failure. Young people may be attracted to violent behavior as a way of asserting their independence of the adult world and its rules, as a way of gaining the attention and respect of peers, as a way of compensating for limited personal competencies, or as a response to restricted opportunities for success at school or in the community. Good relationships with parents during childhood will help in a successful transition to adolescence, but they do not guarantee it.

Adolescents exposed to violence at home may experience some of the same emotions and difficulties as younger school-age children -- for example, fear, guilt, anxiety, depression, and trouble concentrating in school. In addition, adolescents may feel more vulnerable to violence from peers at school or gangs in their neighborhood and hopeless about their lives and their odds of surviving to adulthood. These young people may not experience the growing feelings of competence that are important at their stage of development. Ultimately, their exposure to violence may lead them to become violent themselves. Studies have shown that adolescents exposed to violence are more likely to engage in violent acts, often as preemptive strikes in the face of a perceived threat (Fagan & Wilkinson, 1998; Loeber et al., 1998; Singer et al., 1994, 1995).

Proposed Protective Factors in Childhood and Adolescence

Research on resilience and the public health approach to the problem of youth violence have brought a new awareness of, and research on, protective factors -- those aspects of the individual and his or her environment that buffer or moderate the effect of risk. Identifying and understanding how protective factors operate is potentially as important to violence prevention and intervention efforts as research on risk factors.

To date, the evidence regarding protective factors against violence has not met the standards established for risk factors. Therefore, this report does not refer to protective factors, only to proposed protective factors (Table 4-2). There are several reasons for this: Not all studies define protective factors as buffering the effects of risk; most studies have looked for an effect on antisocial behavior in general, not on violence specifically; and those that have found buffering effects on violence have not been adequately replicated. This does not mean that protective factors do not exist, just that more research is needed to identify them. ⁷

Table

Table 4-2. Proposed protective factors, evidence of buffering risk, and outcome affected, by domain.

Most studies of protective factors do not specify when in the course of development these factors exert their buffering effects or how they change over the life course. Further study is needed to clarify these points; therefore, Table 4-2 does not show age of onset for the proposed protective factors listed.

Conclusions

Scientists have identified a number of personal characteristics and environmental conditions that put children and adolescents at risk of violent behavior and some that seem to protect them from the effects of risk. These risk and protective factors can be found in every area of life, they exert different effects at different stages of development, they tend to appear in clusters, and they appear to gain strength in numbers. The public health approach to youth violence involves identifying risk and protective factors, determining when in the life course they typically come into play, designing preventive programs that can be put in place at just the right time to be most effective, and making the public aware of these findings.

Many years of research have yielded valuable insights into the risk factors involved in the onset and developmental course of violence. Less work has been done on protective factors, but that situation is changing. Some basic principles have emerged from these studies:

• Risk and protective factors exist in every area of life -- individual, family, school, peer group, and community. Individual characteristics interact in complex ways with a child's or adolescent's environment to produce violent behavior.
• Risk and protective factors vary in predictive power depending on when in the course of human development they occur. As children move from infancy to early adulthood, some risk factors will become more important and others less important. Substance use, for example, is a far more powerful risk factor at age 9 than it is at age 14.
• Risk factors do not operate in isolation -- the more risk factors a child or young person is exposed to, the greater the likelihood that he or she will become violent. Risk factors can be buffered by protective factors, however. An adolescent with an intolerant attitude toward violence is unlikely to engage in violence, even if he or she is associating with delinquent peers, a major risk factor for violence at that age.
• Risk factors increase the likelihood that a young person will become violent, but they may not actually cause a young person to become violent. Scientists view them as reliable predictors or even as probable causes of youth violence. They are useful for identifying vulnerable populations that may be amenable to intervention efforts.
• Risk markers such as race or ethnicity are frequently confused with risk factors; risk markers have no causal relation to violence.
• No single risk factor or combination of factors can predict violence with unerring accuracy. Few young people exposed to a single risk factor will become involved in violent behavior; similarly, most young people exposed to multiple risks will not become violent. By the same token, protective factors cannot guarantee that a child exposed to risk will not become violent.
• Researchers have identified at least two onset trajectories for youth violence: a childhood trajectory that begins before puberty and an adolescent one that begins after puberty. Violence peaks during the second decade of life. The small group of offenders who began their violent behavior in childhood commits more violent offenses, and the larger group of adolescent offenders begins to become involved in violence.
• Early risk factors for violence in adolescence include involvement in serious (but not necessarily violent) criminal acts and substance use before puberty, being male, aggressiveness, low family socioeconomic status/poverty, and antisocial parents. All of these early risks stem from a child's individual characteristics and interaction with his or her family. The influence of family is largely supplanted in adolescence by peer influences; thus, risk factors with the largest predictive effects in adolescence include weak social ties to conventional peers, ties to antisocial or delinquent peers, and belonging to a gang. Committing serious (but not necessarily violent) criminal offenses is also an important risk factor in adolescence. Drug selling is a risk factor, but its effect size has not been established.
• Identifying and understanding how protective factors operate is potentially as important to preventing and stopping violence as identifying and understanding risk factors. Several protective factors have been proposed, but to date only two have been found to buffer the risk of violence -- an intolerant attitude toward deviance and commitment to school. Protective factors warrant more research attention.

Violence prevention and intervention efforts hinge on identifying risk and protective factors and determining when in the course of development they emerge. More research in these areas is needed, particularly concerning why violence stops or continues in childhood and adolescence. Nonetheless, the research carried out to date provides a solid foundation for programs aimed at reducing risk factors and promoting protective ones -- and thereby preventing violence, the subject of Chapter 5.

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Appendix 4-Alipsey and Derzon's Classes of Risk Factors

Appendix 4-B Violence in the Media and Its Effect on Youth Violence

Americans have been concerned about the prevalence of violence in the media and its potential harm to children and adolescents for at least 40 years. The body of research on television violence has grown tremendously since the first major Federal reports on the subject in 1972 and 1982 (National Institute of Mental Health, 1982; U.S. Surgeon General's Scientific Advisory Committee on Television and Social Behavior, 1972). During this period, new media emerged -- video games, cable television, music videos, and the Internet. As they gained popularity, these media, along with television, prompted public concern and research attention.

Recent surveys depict the abundance of (primarily electronic) media in U.S. homes (Roberts et al., 1999; Woodard, 1998) and the extensive presence of violence within the media landscape (Wilson et al., 1997, 1998). They also show that the proliferation of new media has expanded the opportunities for children to be exposed to media violence at home. Current psychological theory suggests that the interactive nature of many of these new media may affect children's behavior more powerfully than passive media such as television. Research to test this assumption is not yet well developed, and accurate measurement is needed to determine how much violence children are actually exposed to through various media -- and how patterns of exposure vary among American youths.

In reading this discussion of research on the impact of media violence on America's youth, a few major points should be kept in mind:

• First, research on the effects of media violence examines many kinds of outcomes in young people. Researchers have focused primarily on aggression, an outcome that psychologists define as any behavior, physical or verbal, that is intended to harm another person. Physical aggression may range from less serious acts, such as pushing or shoving, to more serious physical contact and fighting, to very serious violent acts that carry a significant risk of injury or death, such as assault, robbery, rape, and homicide. Some studies have focused on how media violence affects aggressive thinking, including beliefs and attitudes. Other studies have focused on the effects of media violence on aggressive emotions -- that is, on emotional reactions, such as anger, that are related to aggressive behavior. In this discussion, the label "violence" is reserved for the most extreme end of the physical aggression spectrum.
• Second, as noted in Chapter 4, the preponderance of evidence indicates that violent behavior seldom results from a single cause; rather, multiple factors converging over time contribute to such behavior. Accordingly, the influence of the mass media, however strong or weak, is best viewed as one of the many potential factors that help to shape behavior, including violent behavior.
• Third, a developmental perspective is essential for understanding how media violence affects youth behavior and for framing any coherent public health response to it. Although this report focuses generally on the violent behavior of adolescents, it is critical to understand how children are influenced by and respond to media violence, especially in order to recognize and help those who are particularly susceptible to adverse effects. Most youths who are aggressive and engage in some forms of antisocial behavior do not become violent teens and adults. However, it is well established that many violent adolescents and adults were highly aggressive and even violent at younger ages, and the highly aggressive child is at increased risk of growing up to be a more aggressive young adult (Nagin & Tremblay, 1999). Because influences that promote aggressive behavior in some young children can contribute to increasingly aggressive and even violent behavior many years later, it is important to understand the early factors that may play a role in later outcomes.
• Fourth, a growing body of research supports theories that explain how exposure to media violence would activate aggressive behaviors or attitudes in some children. Humans begin imitating other individuals at a very early age, and young children learn many motor and social skills by observing the behavior of others (Bandura, 1977). Social interactions shape the scripts for behavior that children acquire, but observational learning is a powerful mechanism for acquiring social scripts throughout childhood (Huesmann, 1998). Most researchers agree that such observational learning is probably the major psychological process underlying the effects of media violence on aggressive behavior. This same process could explain how prosocial behavior depicted in the media might encourage positive behavior in children (Friedlander, 1993; Harold, 1986; Mares, 1996).

Media Violence: Exposure and Content

American children and youths spend, on average, more than 4 hours a day with television, computers, videotaped movies, and video games (Roberts et al., 1999; Woodard, 2000). But their exposure to media varies considerably, depending on their age, parental viewing habits, and family socioeconomic status (SES). Most systematic research on children's exposure to violent media dates back to the 1970s, when most families did not have access to cable television, music videos, video games, or the Internet. As noted earlier, very few contemporary studies systematically document children's actual consumption of violent media; this is particularly true for the newer media.

Several content analyses over the last 30 years have systematically examined violence on television (Gerbner et al., 1980; Potter et al., 1995; Signorielli, 1990). The largest and most recent of these was the National Television Violence Survey (NTVS) ¹ (Wilson et al., 1997, 1998), which examined the amount and content of violence ² on American television for three consecutive years, as well as contextual variables that may make it more likely for aggression and violence to be accepted, learned, and imitated. Smith and Donnerstein (1998) report the following NTVS findings:

• 61 percent of television programs contain some violence, and only 4 percent of television programs with violent content feature an "antiviolence" theme.
• 44 percent of the violent interactions on television involve perpetrators who have some attractive qualities worthy of emulation.
• 43 percent of violent scenes involve humor either directed at the violence or used by characters involved with violence.
• Nearly 75 percent of violent scenes on television feature no immediate punishment for or condemnation of violence.
• 40 percent of programs feature "bad" characters who are never or rarely punished for their aggressive actions.

The NTVS report notes that many television programs fail to depict the harmful consequences of violence. Specifically, it finds that of all violent behavioral interactions on television, 58 percent depict no pain, 47 percent depict no harm, and 40 percent depict harm unrealistically. Of all violent scenes on television, 86 percent feature no blood or gore. Only 16 percent of violent programs feature the long-term, realistic consequences of violence.

Major Behavioral Effects of Media Violence

Because an exhaustive description of the research literature is not possible within this brief discussion, findings from meta-analyses are reported ³ where available. In meta-analyses, the results of multiple studies are combined and compared systematically and an overall effect size computed. These analyses include findings from randomized experiments that look at aggression immediately after viewing violence, as well as cross-sectional surveys that provide a snapshot of the relationship between viewing violence and behavior at a fixed point in time. Also presented are findings from longitudinal studies that examine whether exposure to media violence affects violence and aggression over time.

Summary of Major Empirical Research Findings

A substantial body of research now indicates that exposure to media violence increases children's physically and verbally aggressive behavior in the short term (within hours to days of exposure). Media violence also increases aggressive attitudes and emotions, which are theoretically linked to aggressive and violent behavior. Findings from a smaller body of longitudinal studies suggest a small but statistically significant impact on aggression over many years. The evidence for long-term effects on violence is inconsistent.

Based on the findings of studies reported here, the average effect sizes of exposure to media violence on various measures of aggression range from small (r = .15) to quite large (r = .64). The evidence that exposure to media violence is a risk factor for violent behavior is more limited, with small average effect sizes of r = .06 in cross-sectional surveys, r = .13 in experimental studies (Paik & Comstock, 1994), and r = .00 to .22 in longitudinal studies (Huesmann et al., (submitted); Milavsky et al., 1982). Taken together, findings to date suggest that media violence has a relatively small impact on violence. The effect on aggression is stronger, ranging from small to moderate.

Although there is clear scientific evidence of a correlation between exposure to media violence and some violent behaviors, randomized experiments -- the research methodology best suited to determining causality -- cannot ethically be used in studies of violent behavior. Thus, the causal links between media violence and behavior are more firmly established for aggressive behavior than for violent behavior. Longitudinal studies, which also provide some insights into this issue, have linked repeated exposure to media violence in the early years with an increased likelihood of aggressive behavior in the teen and adult years. However, few of these studies have reported on violence as an outcome. Moreover, the violent behaviors that are the focus of this report (homicide, forcible rape, aggravated assault, and robbery) occur infrequently and are subject to multiple influences. At present, it is extremely difficult to distinguish between the relatively small, long-term effects of media exposure and those other influences.

In sum, a diverse body of research provides strong evidence that exposure to violence in the media can increase children's aggressive behavior in the short term. Some studies suggest that long-term effects exist, and there are strong theoretical reasons why this is the case. But many questions remain regarding the short- and long-term effects of media violence, especially on violent behavior. Despite considerable advances in research, it is not yet possible to describe accurately how much exposure, of what types, for how long, at what ages, for what types of children, or in what types of settings will predict violent behavior in adolescents and adults.

Preventive Efforts

Efforts to reduce the presumed harmful effects of media violence on youths have taken various forms, including:

• Attempting to reduce the amount of media violence and children's access to it (for example, calls for media self-regulation and violence ratings);
• Encouraging and facilitating parental monitoring of children's access to media (for example, V-chip legislation and advisory labels on music and video games);
• Educating parents and children about the potential dangers of media violence (for example, media and empathy educational programs); and
• Targeting children's views about violence to reduce the chances that they will imitate the violence they see (Corder-Bolz, 1980; Hicks, 1968; Huesmann et al., 1983; Linz et al., 1990; Nathanson, 1999).

From a public health perspective, this preventive domain is largely uncharted territory. Few preventive efforts have been studied systematically. Furthermore, not enough research has been done to form a basis for the design of many experimental interventions. As noted in other parts of this report, an extensive body of scientific research undergirds our emerging knowledge about effective ways of preventing youth violence. Although many violence prevention programs address a complex array of risk and protective factors in the lives of young people, they have not yet addressed the role of the media. This gap needs to be filled.

Implications

Research to date justifies sustained efforts to curb the adverse effects of media violence on youths. Although our knowledge is incomplete, it is sufficient to develop a coherent public health approach to violence prevention that builds upon what is known, even as more research is under way. Unlike earlier Federal research reports on media violence and youth (National Institute of Mental Health, 1982; U.S. Surgeon General's Scientific Advisory Committee on Television and Social Behavior, 1972), this discussion takes place within a broader examination of the causes and prevention of youth violence. This context is vital. It permits media violence to be regarded as one of many complex influences on the behavior of America's children and young people. It also suggests that multilayered solutions are needed to address aggressive and violent behavior.

A variety of media violence is present in the homes of young children, with considerable variation in the degree of parental supervision (Woodard, 1998). Regardless of government and other interested groups' attempts to limit the amount of violence reaching American families, families themselves play a critical role in guiding what reaches their children. Whether by adopting V-chip technology for home television programming, by using Internet violence screening, or simply by monitoring closely children's use of televisions, computers, and video games, parents can limit and shape their children's selection of, interaction with, and response to media violence. Community groups -- including schools, faith-based organizations, and Parent Teacher Associations -- can teach parents and children how to be more critical consumers of media. Federal agencies can be more active in encouraging needed research, in sharing research findings with the public, in encouraging increased interaction between violence prevention researchers and media researchers, and in creating networks for sharing solutions to social and public health problems.

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Footnotes

1

If the relationship to violence is nonlinear, risk and protection may take on a different meaning. However, the conditions and characteristics identified as protective factors by those using the absence-of-risk conceptualization rarely, if ever, involve a nonlinear relationship to violence.

2

As noted in Chapter 3, most violent offenders commit many serious property offenses (such as burglary, auto theft, and larceny), and most youths involved in serious property offenses (FBI index offenses) are also involved in violent offenses. The risk factors described here are based on longitudinal studies that use self-reports to predict violent offenses. Several of the studies also include official arrest data and thus predict self-reported offenses, arrests for serious or violent offenses, or both.

3

Effect sizes for risk factors not included in the meta-analyses reported by Lipsey and Derzon (1988), Hawkins et al. (1998c), and Parik and Comstock (1994) are weighted (by sample size) mean correlations. The effect sizes in Parik and Comstock are unweighted mean correlations.

4

Numerous studies of these effects have been done, notably those of Robert Pynoos and colleagues. See, for example, Pynoos, R. & Nader K. (1988). Psychological first aid for children who witness community violence. Journal of Traumatic Stress, 1, 445-473.

5

This is a different use of the term "risk marker" than that proposed by Kraemer et al. (1997). They use risk marker to refer to a risk factor or cause (such as sex or race) that cannot, in practical terms, be changed by an intervention. This report focuses on its causal role rather than its amenability to change.

6

In another study, the relative risk of later violence was two to three times as great among abused children as nonabused children (Zingraff et al., 1993).

7

There is a fairly extensive body of research on protective factors in the field of psychopathology (Garmezy, 1985; Rae-Grant et al., 1989; Rolf et al., 1993; Rutter, 1979, 1985; Rutter et al., 1979; Stattin et al., 1997; Werner and Smith, 1982, 1992). There are also a number of studies focusing on delinquency that purport to identify protective factors (Brewer et al., 1995; Farrington and West, 1993; Hawkins et al., 1992; Resnick et al., 1997; Smith et al., 1995).

1

The NTVS randomly sampled programs from 6:00 a.m. to 11:00 p.m. on 23 broadcast and cable channels over a 20-week period from October to June during the 1994 through 1997 viewing seasons. A sum of 119 hours per channel, or 2,500 hours of television programming, was assessed each year.

2

The NTVS defined violence as "overt depiction of a credible threat of physical force, or the actual use of such force intended to physically harm an animate being or group of beings." Content analyses of television programs generally treat the program itself as the unit of analysis and exclude advertisements. "Violence also includes certain depictions of physically harmful consequences against an animate being or group that occur as a result of unseen violent means. Thus, there are three primary types of violent depictions: credible threats, behavioral acts, and harmful consequences" (Smith & Donnerstein, 1998, p. 170).

3

In the text to follow, all reported results are statistically significant (p < .05).

4

In this study, all effects are unweighted average effects.

5

These predictions are based on subsamples from which many of the most aggressive children had been dropped by the research team, reportedly because they were not accurately describing their television viewing.