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Chapter 4
Risk Factors for Youth Violence
Research has documented the magnitude of youth violence and the trends in that violence
over time. But what do we know about why young people become involved in violence?
Why do some youths get caught up in violence while others do not? There is no simple
answer to these questions, but scientists have identified a number of things that put
children and adolescents at risk of violent behavior and some things that seem to protect
them from the effects of risk.
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).
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 violenceessential
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.
Box 4-1: Early and late risk factors for violence at age 15 to 18 and proposed protective factors, by domain
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 behaviorto
have learned violent behavior from themthan simply to have inherited it from them.
Likewise, societys differing expectations of boys and girlsexpecting boys to
be more aggressive, for examplecan 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 effectsthat 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
developsone 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 behaviorone 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 adolescencethat 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 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 violencefor 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 developmentand
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.
Protective Factors
There is some disagreement about exactly what protective factors are. They have been
viewed both as the absence of risk and as something conceptually distinct from risk
(Guerra, 1998; Jessor et al., 1995; Reiss & Roth, 1993; Wasserman & Miller, 1998).
The former view typically places risk and protective factors on the opposite ends of a
continuum. For example, good parent-child relations might be considered a protective
factor because it is the opposite of poor parent-child relations, a known risk factor. But
a simple linear relationship of this sort (where the risk of violence decreases as
parent-child relations improve) blurs the distinction between risk and protection, making
them essentially the same thing.1
The view that protection is conceptually distinct from risk (the view used in this
report) defines protective factors as characteristics or conditions that interact with
risk factors to reduce their influence on violent behavior (Garmezy, 1985; Rutter, 1985;
Stattin & Magnusson, 1996). For example, low family socioeconomic status is a risk
factor for violence, and a warm, supportive relationship with a parent may be a protective
factor. The warm relationship does not improve the childs economic status, but it
does buffer the child from some of the adverse effects of poverty. Protective factors may
or may not have a direct effect on violence (compare Jessor et al., 1995 and Stattin &
Magnusson, 1996).
Interest in protective factors emerged from research in the field of developmental psychopathology. Investigators observed that children with exposure to multiple risk factors often escaped their impact. This led to a search for the characteristics or conditions that might confer resiliencethat is, factors that moderate or buffer the effects of risk (Davis, 1999; Garmezy, 1985; Rutter, 1987; Werner, 1989). Protective factors offer an explanation for why children and adolescents who face the same degree of risk may be affected differently.
The concept of protective factors is familiar in public health. Wearing seat belts, for example, reduces the risk of serious injury or death in a car crash. Identifying and measuring the effects of protective factors is a new area of violence research, and information about these factors is limited. Because they buffer the effect of risk factors, protective factors are an important tool in violence prevention.
Like risk factors, proposed protective factors are grouped into individual, family,
school, peer group, and community categories. They may differ at various stages of
development, they may interact, and they may exert cumulative effects (Catalano et al.,
1998; Furstenberg et al., 1999; Garmezy, 1985; Jessor et al., 1995; Rutter, 1979; Sameroff
et al., 1993; Thornberry et al., 1995). Just as risk factors do not necessarily cause an
individual child or young person to become violent, protective factors do not guarantee
that an individual child or young person will not become violent. They reduce the
probability that groups of young people facing a risk factor or factors will become
involved in violence.
A Note on Sources
This chapter draws heavily on four important studies: Lipsey & Derzons meta-analysis of 34 longitudinal studies on risk factors for violence (1998); Hawkins et al.s study of malleable risk and protective factors drawn from 30 longitudinal studies, including some not included in the Lipsey & Derzon meta-analysis (Hawkins et al., 1998c); Paik and Comstocks meta-analysis of 217 studies of exposure to media violence and its effects on aggression and violence (1994); and the National Institute of Mental Healths Taking Stock report (Hann & Borek, in press), an extensive
review of research on risk factors for aggression and other behavior problems.
Table 4-1 is adapted from the tables presented in the Lipsey and Derzon and
Hawkins et al. meta-analyses. The risk factors in Table 4-1 predict
feloniesthat is, violent and property crimesat ages 15 to 18, the peak years
of involvement.2 Entries in bold are effect sizes from the meta-analyses by Lipsey and
Derzon, Hawkins et al., and Paik and Comstock for various classes of risk factors; other
entries are effect sizes reported in two or more longitudinal studies. (Risk classes are
described in Appendix 4A and later sections of this chapter.) Some of the risk
classes in Table 4-1 include several separate risk factors. For example,
psychological condition includes hyperactivity, daring, and attention problems.
Additional risk factors and classes of risk factors have been added from other sources.
For example, there is adequate evidence to establish harsh, lax, or inconsistent
discipline as a separate risk factor, although Lipsey and Derzon include it in the poor
parent-child relations class. Academic failure, family conflict, and belonging to a gang
are additional examples of risk factors not included in any of the meta-analyses.
The measure of effect size used in these tables is a bivariate correlation (r), or simple correlation between two variables.
All estimates of effect size are statistically significant and are based on multiple
studies, with those for risk classes typically involving more studies than those for
separate risk factors. The studies reviewed in Lipsey and Derzon, Paik and Comstock, and
Hawkins et al. are not cited here; however, other studies that were used to establish a
risk factor or that are included in estimates of effect size are cited.3
There is a rich and extensive body of research on risks for antisocial behavior,
externalizing behavior, conduct disorder, and aggression (Hann & Borek, in press).
Each of these terms defines a pattern or set of behaviors that includes aggressive or
violent behavior, but most of the behaviors included are either nonphysical, nonviolent
acts or relatively minor forms of physical aggression. Risk factors for antisocial
behavior may be quite different from those that predict violent behavior (robbery,
aggravated assault, rape, and homicide). Since antisocial behavior does not present the
potential for serious injury or death that violence does, this report relies on studies
that identify risk factors for serious offenses generally and violent behavior
specifically, bearing in mind that the vast majority of serious offenders report having
been involved in violent offenses.
Summary
Risk and protective factors can be found in every area of a child or adolescents
life, they exert different effects at different stages of development, and they gain
strength in numbers. The public health approach to the problem of youth violence seeks to
identify risk and protective factors, determine when in the life course they typically
occur and how they operate, and enable researchers to design preventive programs to be put
in place at just the right time to be most effective.
This chapter describes what is known about individual, family, school, peer group, and
community risk and protective factors that exert their effects in childhood and
adolescence. It describes the power of early risk factors, which come into play before
puberty, and late risk factors, which exert their influence after puberty, to predict the
likelihood of youth violence.
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. |
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