Youth Violence Glossary
Absolute deterrent effects. Effects that are demonstrated when an intervention
produces better outcomes compared to no treatment.
Age of onset (of serious violence). The age at which an individual reports his
or her first act of serious violence.
Age-specific prevalence. The proportion of youths at any given age who report
having committed at least one serious violent act in the past year.
Aggravated assault. An unlawful attack by one person upon another wherein the
offender uses a weapon or displays it in a threatening manner, or the victim suffers
obvious severe or aggravated bodily injury involving apparent broken bones, loss of teeth,
possible internal injury, severe laceration, or loss of consciousness. Along with
homicide, robbery, and rape, one of the four violent crimes covered in this report.*
Aggression (aggressive behavior). Behavior, physical or verbal, that is intended
to harm another person.
Antisocial attitudes. Favorable attitudes toward violence, dishonesty, and rule
breaking with hostility toward authority.
Antisocial behaviors. Problem behaviors that range from relatively minor acts
such as lying, stealing, truancy, disobedience, and temper tantrums to serious nonviolent
or violent behavior such as burglary or aggravated assault.
Attention-deficit/hyperactivity disorder (ADHD). A cognitive disorder
characterized by restlessness, excessive activity, and difficulty paying attention.
Career length. Variously defined as the number of years of active offending; or
the maximum number of consecutive years of offending; or the span between the first and
last year during which a youth meets the criteria for a serious violent offender.
Case study research. A type of study design involving multiple observations of a
single individual over time.
Chronic offenders. Variously defined by some minimum number of offenses; for
example, youths with three or more serious violent offenses per year.
Contagion effect (of violence). Unproved notion that seeing or hearing about
violence in news coverage encourages violent or aggressive behavior.
Control group. A group that receives standard care or no intervention in a
research study, compared to the experimental, treatment, or intervention group.
Co-occurrence (of problem behaviors). The simultaneous display of violence and
other problem behaviors (e.g., substance use, property crimes, gun ownership). Although
these behaviors occur together, it cannot be assumed that one behavior causes another.
Conduct disorder. Childhood disorder marked by persistent acts of aggressive or
Cross-sectional research. A type of study design, frequently used in public
opinion polls, surveys, and epidemiological research. It involves a single contact with
participants for data collection at a given point in time and thus does not permit
researchers to estimate individual-level change, development, or predictive effects of a
given risk or protective factor on later violent behavior.
Cumulative prevalence (lifetime prevalence or ever-prevalence). The proportion
of youths at any particular age who have ever committed a serious violent offense.
Delinquent (antisocial) lifestyle. A pattern of consciously chosen and sustained
behaviors that include antisocial or illegal acts, typically involving property crimes,
substance use, gun ownership, and promiscuity.
Deterrent effects (absolute). See Absolute deterrent effects.
Deterrent effects (marginal). See Marginal deterrent effects.
Developmental perspective (on youth violence). An approach to understanding youth
violence that considers the complex interaction of individuals with their environment at
particular times in their lives; this approach recognizes that patterns of behavior change
over the life course.
Developmental trajectory (course, pathway, or progression) of violent behavior.
The distinct pattern of violent behavior that emerges for an individual over time.
Does Not Work program. Prevention programs in this category demonstrate
consistent evidence of no effects or harmful effects.
Early-onset trajectory. A pattern of violent behavior that emerges before
adolescence, defined in this report as about age 13. In this pathway, problem behaviors in
childhood gradually escalate over time to more violent ones, culminating in serious
violence before adolescence. This pattern is less prevalent than the late-onset trajectory
and is characterized by higher offending rates, greater seriousness of adolescent
offenses, and greater persistence of violence from adolescence into adulthood.
Effect size. The predictive power of an individual or general type of risk or
protective factor; or the size of the deterrent effect of an intervention compared to no
treatment or a standard treatment. The measure used for risk factor effect sizes in this
report is a simple correlation between two variables. For program effectiveness, the effect size
measure is the average difference (standardized) between the treatment and control group
means on the selected recidivism measure.
Effectiveness trials. Research that tests for benefits to participants in a
natural or applied setting.
Efficacy trials. Research that tests for benefits to participants in a
controlled or experimental setting.
Epidemiology. Study of the factors influencing the incidence, frequency, and
distribution of health-related events in the population; identifying appropriate risk and
protective factors for prevention and intervention programs.
Experimental research. A type of study design involving comparison of a group
that receives an intervention (experimental or treatment group) and a group that receives
standard care or no intervention (control group) in which participants are randomly
assigned to one of these groups. This study design permits researchers to assess
cause-and-effect relationships and can be used to determine intervention effectiveness.
Externalizing symptoms. A behavioral pattern characterized by the acting out of
Hazard rate. The proportion of individuals who initiate a given behavior (e.g.,
serious violence) at a given age.
Homicide. The willful (nonnegligent) killing of one human being by another;
along with robbery, aggravated assault, and rape, one of the four violent crimes covered
in this report.*
Iatrogenic. In the context of youth violence, interventions that are harmful or
actually increase involvement in violence.
Incident rate. The number of self-reported violent acts within a given-sized
population, a measure of the volume of violence; as used in this report, the number of
violent acts per 1,000 young people.
Intervention. See Secondary prevention.
Late-onset trajectory. A pattern of violent behavior that emerges in adolescence,
defined in this report as about age 13. This pattern is more prevalent than the
early-onset trajectory and is characterized by a shorter period of involvement, lower
frequency of offending, and a lower likelihood of continuing into adulthood. Individuals
who are characterized by this pattern typically give few external signs in childhood that
they will become violent offenders.
Level of control. Efforts to take into account other factors that might
influence the data or responses from participants in a research study; contributes to the
quality of a given study.
Level of evidence. The strength of the evidence amassed for any scientific fact
Lifestyle. A pattern of consciously chosen, observable behaviors that a person
engages in on a consistent and regular basis.
Locally representative (probability) sample. In this report, the term representative
sample is used to refer to a probability samplea sample that is selected
in such a way that its characteristics can be generalized to the population (e.g., city or
county) from which it was drawn with a known degree of accuracy. The accuracy of
generalizations from probability samples is given in the form of a confidence interval. In
this report, 95 percent confidence intervals (CIs) are reported, indicating an upper and
lower bound for the population estimate that is accurate at least 95 percent of the time.
Longitudinal research. Used in etiological (causal) and developmental research,
a type of study design involving multiple contacts with the same study participants over
time; allows researchers to estimate how well a given risk or protective factor predicts
later violent behavior for individuals or groups.
Marginal deterrent effects. Effects that are demonstrated when an intervention
produces significantly better outcomes compared to another treatment; may underestimate
the true effects of the intervention compared to receiving no treatment at all.
Maturation effect. An effect associated with growing older or maturing, it may
refer to changes in ones physical or social development. The term refers
specifically to a sharp reduction in youth violence observed during the transition to
adulthood, usually during the late teen years to age 20.
Mediating-effects analysis. An analysis that permits researchers to determine
whether a change in the targeted risk or protective factor accounts for an observed change
Meta-analysis. A rigorous statistical method of combining the results of several
studies to obtain more reliable estimates of the effects of a general type of treatment or
intervention; can be used to summarize program evaluation and draw overall conclusions
about the strength and consistency of the influence, or effect size, that particular types
of programs have on violence.
Model program. A prevention program that meets the highest scientific standard
for effectiveness, as evidenced in published evaluations; has a significant, sustained
preventive or deterrent effect and has been replicated in different communities or
settings. It has been shown to work and can be expected to have a positive result in a
wide range of community settings.
Monitoring the Future (MTF). A cross-sectional survey of high school seniors
that obtains self-reports about a wide range of social attitudes and behaviors, including
drug use and violence. This study has been conducted annually since 1975 by the University
of Michigans Institute for Social Research and is the longest-running national
survey of its type. It also has a longitudinal component, following high school seniors
into their adult years, but little has been published on the longitudinal data.
National Crime Victimization Survey (NCVS). A national, self-report, household
survey conducted by the Bureau of Justice Statistics that provides annual estimates of
levels and rates of criminal victimization in the United States. Residents of selected
households age 12 and older are interviewed about their victimization experiences,
including serious violent assaults, rapes, and robberies and whether they reported these
crimes to law enforcement officials.
National Electronic Injury Surveillance System (NEISS). Operated by the U.S.
Consumer Product Safety Commission since 1992, the system monitors types of injuries
treated in emergency departments, including those related to firearms.
National Television Violence Survey (NTVS). A recent content analysis of
television programming examining its portrayal of violence. The study assessed a total of
2,500 hours of television programming during the 1994 through 1997 viewing seasons.
National Youth Survey (NYS). A national, longitudinal study of U.S. youths age
11 to 17 begun in 1976. Study participants have been interviewed nine times, with the last
interviews completed in 1993. The study includes both self-reported and official police
records. Measures of a wide range of delinquent, violent, and drug-using behaviors, as
well as conventional behaviors, are obtained in confidential interviews.
Nationally representative sample. A probability sample of a country, such as the
United States or the United Kingdom. A sample drawn in such a way that its characteristics
can be generalized to the U.S. population with a known degree of accuracy (confidence
interval). See Locally representative sample.
Personality disorders. Behavior syndromes characterized by maladaptive personality
patterns that result in chronically dysfunctional perceptions, thoughts, and behaviors.
Physical aggressiveness. Relatively nonserious forms of violent behavior, often
displayed in early childhood and continued into adolescence, including hitting, biting,
kicking, punching, or otherwise intentionally hurting others.
Population-based studies. Studies based on general population samples rather
than selected or institutional samples (e.g., prisoners, hospital patients, nursing home
residents, expelled students). Findings from these studies apply to general populations,
whereas findings from studies of selected or institutional samples apply specifically to
persons in these settings or groups.
Post-traumatic stress disorder (PTSD). Disorder in which a stressful experience
is traumatic and produces severe, recurring symptoms.
Prevalence rate. As used in this report, the proportion of youths involved in
one or more violent behaviors during some specified time interval, for example, the past
year, by age 18, or ever.
Primary prevention (true prevention). As defined in this report, strategies and
programs that reduce the likelihood that youths will initiate violent behavior compared to
youths in a control group; programs designed to target youths who have not yet become
involved in violence or encountered specific risk factors for violence; identifies
behavioral, environmental, and biological risk factors associated with violence and takes
steps to educate individuals and communities about and protect them from these risks.
Probability sample. A sample selected in such a way that its characteristics can
be generalized to the population from which it was drawn with a known degree of accuracy.
The level of accuracy for proportions, means, and correlations is presented as a 95
percent confidence interval, which contains the true population value 95 percent of the
time. See Locally representative sample.
Promising program. Prevention programs in this category meet two of the scientific
standards for effectiveness; they do not meet all of the rigorous standards of Model
programs, but they are recognized and encouraged with the caution that they be carefully
Protective factor. As used in this report, personal characteristics or
environmental conditions that reduce the potential harmful effect of a risk factor for
violent behavior; characteristics that buffer or moderate the effect of risk. Protective
factors are grouped into individual, family, school, peer group, and community domains.
Public health approach. A practical, goal-oriented, and community-based approach
to promoting and sustaining health. This approach 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 that are effective in reducing risk and
Quasi-experimental research. A type of study design with experimental and
control groups but without random assignment to these groups. Groups are matched on
selected characteristics, or differences are controlled in the analysis. The claim of
group equivalence or comparability is not as strong with this design as in an experimental
Rape (forcible rape). The carnal knowledge of a person, forcibly and/or against
that persons will; or not forcibly or against the persons will where the
victim is incapable of giving consent because of his or her temporary or permanent mental
or physical incapacity (or because of his or her youth). Along with homicide, robbery, and
aggravated assault, one of the four violent crimes covered in this report.*
Reliability (of research instruments or measures). The consistency of a measure;
the measure yields the same result on different occasions or applications (when no real
change has occurred).
Replication. Repeating an intervention or prevention program at multiple sites
to determine if the results will be the same; establishes that a program can be effective
at other sites when implemented by new teams under different conditions.
Risk factor. In the context of youth violence, personal characteristics or
environmental conditions that increase the likelihood that a young person will become
violent but that may not actually cause a person to become violent. Risk factors are
grouped into individual, family, school, peer group, and community domains. The more risk
factors a young person is exposed to, the greater the likelihood that he or she will
Risk marker. A personal characteristic or environmental condition associated
with known risk factors but having no causal relation to violence on its own.
Robbery. The taking or attempting to take anything of value from the care,
custody, or control of a person or persons by force or threat of force or violence and/or
putting the victim in fear. Along with homicide, aggravated assault, and rape, one of the
four violent crimes covered in this report.*
Sampling. The selection of persons to be studied in a research project.
Schizophrenia-spectrum disorders. Broad category of disorders that includes
individuals with symptoms such as serious distortions of reality (including hallucinations
and delusions), withdrawal from social interaction, and disorganization and fragmentation
of perception, thought, and emotion, for which other plausible explanations could be
Secondary prevention. In the context of this report, strategies and programs
that reduce the risk of violence among youths who display one or more risk factors for
violence (high-risk youths).
Self-directed violence. Self-inflicted injury and suicide; not the focus of this
Self-report studies. Research that asks people in confidence to describe their
own behavior. In the context of youth violence, surveys that ask young people in
confidence about violent acts they have committed or have been victims of during a given
period of time.
Serious violent crime (serious violence or index crimes). As defined in this
report, aggravated assault, robbery, rape, and homicide.
Serious violent youths. Youths involved in serious violent behavior (crimes).
They are typically high-frequency offenders who are involved in both serious and
nonserious offenses. These youths account for a major share of all criminal behavior by
persons under age 18.
Socially disorganized community. A community characterized by high levels of
poverty, unemployment, high turnover of residents, and a large proportion of disrupted or
Socioeconomic status. In reference to youths, their parents education,
occupation, and income.
Statistical significance. The level of confidence with which one can conclude
that a difference between two or more groups (generally a treatment and control group) is
the result of the treatment delivered rather than the selection process or chance. A
probability value of .05 is widely accepted as the threshold for statistical significance
in the social and behavioral sciences; a probability value below this threshold (p
< .05) indicates that a difference of this magnitude could happen by chance less than 5
percent of the time.
Superpredators. A new breed of violent youths who commit more frequent and
vicious violent crimes, without remorse, than in previous generations. Contrary to a
recent myth, there is no evidence that this type of violent youths emerged in the 1990s.
Surveillance. A type of research that establishes the nature of a health
problem, describes its incidence and prevalence trends, and monitors its magnitude over
time. Public health specialists use this information to determine appropriate prevention
and intervention efforts.
Sustained effects. Changes in individual competencies and environmental
conditions produced by effective programs that last at least a year beyond treatment or
participation in the intervention.
Tertiary prevention. In the context of this report, strategies and programs that
prevent further violence or the escalation of violence among youths already involved in
Uniform Crime Reporting (UCR) program. Operated by the FBI since the 1930s, the
program monitors arrests made by law enforcement agencies across the United States and
compiles annual arrest information.
Validity (of research instruments or measures). The degree to which an
instrument tests what it is supposed to test, or a measure assesses what it is supposed to
Wraparound services. An approach that is designed to tailor social services to
Youth Risk Behavior Survey (YRBS). A national school-based survey conducted
biannually by the Centers for Disease Control and Prevention in collaboration with
Federal, state, and private-sector partners since 1990. The survey monitors six important
health behaviors, including those that may result in violent injuries among both public
and private school students in grades 9 to 12. The survey is voluntary, is anonymous,
provides for parental consent for minors, and oversamples minorities.