Nearly all homicides are reported to health and safety officials and are counted in public data sources, but nonlethal violence is often unreported (eFigure 1 in the Supplement). For example, in 2011, approximately 1570 children younger than 18 years died from child maltreatment.¹⁸ In that year more than 3 million children received an investigation or response from state child protective services departments,¹⁸ but it is estimated that most episodes of child maltreatment were not reported. National survey data from 2011 estimate that 13.8% of children (calculated to be >10 million youth), had experienced some form of maltreatment by a caregiver.¹⁹ Child maltreatment can go undetected for a considerable amount of time; clinicians must be vigilant to avoid missed opportunities for detection and referral by recognizing symptoms and signs of maltreatment in clinical encounters.²⁰

Violence toward adults is also underreported. Survey data from the National Intimate Partner and Sexual Violence Survey estimate that more than 12 million women and men report experiencing some form of violence (rape, physical violence, or stalking) by an intimate partner each year, but only approximately 480 000 injuries are reported to police annually and 150 000 injuries receive medical treatment (eFigure 2 in the Supplement). The US Justice Department surveillance systems indicate that other forms of violent crime are underreported as well (eFigure 3 in the Supplement).

One reason that violence is underrecognized is that violence reporting systems are compartmentalized; the CDC’s National Violent Death Reporting System synthesizes information from several sources of data, but it only covers deaths and is currently operational in only 32 states. Medical, public health, police, judicial, child welfare, educational, correctional, and community agencies and organizations have also not yet built mechanisms for comprehensive, coordinated responses to violence.

Many forms of violence are interconnected at the individual level, across relationships and communities, and even intergenerationally. Traditionally, efforts to understand, prevent, and respond to interpersonal violence have been constrained by the way violence has been categorized—usually in terms of the relationship between the perpetrator and the survivor (eg, parent or caregiver-child, peer to peer, partner or spouse), but different categories of violence have similar risk factors or protective factors. A survivor of violence may also be a violence perpetrator.²¹ Individuals experience multiple forms of violence and some perpetrators may perpetrate multiple types of violence.²² A family may experience both child maltreatment as well as partner violence,²³ and perpetrators of family violence may also be violent toward nonfamily members.²⁴ Exposure to violence as a child (either directly or as a witness) is a strong and consistent predictor of future violence exposure as an adolescent or adult as well as the perpetration of violence as an adolescent or adult.^25,26

Table 2 shows select risk factors that may influence the perpetration of multiple forms of violence at different levels of the social ecology—individual, family, community, and society. With regard to individual-level risk factors for violence, there are certain neuropsychological deficits, such as hostile attributional biases and poor impulse control, that can be present among perpetrators of different forms of violence.^27–29 For example, poor impulse control can involve problems with excessive anger or hyperreactivity to a given stimulus, such as a child crying.²⁷ In meta-analyses, poor impulse control is associated with a 0.34 correlation with physical child abuse perpetration and a 0.15 correlation with youth violence perpetration.^27,28 These types of processing deficits may result from exposure to chronic stressors prenatally or in early childhood affecting the volume, connectivity, and chemistry of the brain. Though these changes do not directly lead to violence perpetration, they can leave an individual impaired in many areas of functioning, which can contribute to violence involvement. For example, with hostile attributional biases, individuals may incorrectly perceive an offense to themselves where none was intended—such as a youth who interprets a glance from peers or a collision in the hallway with another student to be a threat, where no insult was actually intended (correlation coefficient for youth violence of 0.13).

There are many causes of stressors to children that can affect brain development or are associated with violence perpetration later in life, including child maltreatment and witnessing partner violence. Chronic stressors may result from living conditions that affect children directly, such as poverty. At the societal level, high levels of income inequality have been linked to multiple forms of violence. A study of income inequality across 3142 US counties detected a 0.17 correlation between county-level income inequality and official child maltreatment reports; cross-national studies have also found significant associations between income inequality and other forms of violence.^34–36 Additionally, stressors can occur indirectly by means of their effects on parental well-being and parenting behaviors. Structural disadvantage and racism can also contribute to the perpetration of multiple forms of violence.³⁸ Although most of the risk factors listed in Table 2 are associated with chronic stress in the lives of children, it is important to note that the variance explained by any 1 risk factor is generally small. Consequently, although these risk factors should be considered in exploring opportunities for prevention, intervening solely on 1 risk factor may have limited effect. Research suggests that it is the accumulation of multiple adverse experiences that is associated with the greatest risk of subsequent likelihood of violence involvement. In contrast to the effect of risk factors, adverse health outcomes may be buffered by protective factors, such as safe, stable, and nurturing family relationships and high levels of support and cohesion within communities.³¹

The proportion of assaults resulting in the death of an individual (ie, the case-fatality rate) has declined markedly since the 1960s (Figure). This decline in the lethality of assaults is believed to be largely attributable to improvements in the quality and availability of trauma care. Over the past several decades, the number of hospitals, hospital capacity, physician availability and specialization, and technology used in caring for individuals who are critically ill has improved and such measures have been associated with lethality reductions on the county level.⁵ Injured patients receiving care at trauma centers have a lower risk of death than those treated at other facilities.⁴² However, since the mid-1990s, decreases in case-fatality rates have slowed (Figure). It appears that there is a limit to which skilled critical care can save patients’ lives; clinicians and health care systems should consider ways to become more involved in violence prevention.

Beyond physical injuries, which are the most apparent consequences of violence, the association between violence and infectious diseases, especially sexually transmitted infections (STIs) such as human immunodeficiency virus (HIV), is well established.^43,44 For example, although forced sexual intercourse can directly transmit infectious agents, sexual and nonsexual violence are also associated with subsequent early sexual debut, multiple partners, failure to use condoms or other forms of protection, and other behaviors that increase the risk of STIs. In a recent meta-analysis, relative to children experiencing no abuse, the odds of contracting STIs or engaging in risky sexual behaviors ranged from 57% higher among those children experiencing neglect to 78% higher among children experiencing physical abuse.⁴⁴ Beyond the risk of STIs, exposure to abuse as a youth is also associated with adverse reproductive health outcomes, including fetal death and postpartum depression.⁴⁵

Experiencing violence (physical, sexual, psychological) is associated with increased risks of mental health and behavioral disorders such as depression, posttraumatic stress disorder, personality and conduct disorders, anxiety, sleep and eating disorders, substance abuse, and suicide and suicide attempts.⁴⁶ For example, meta-analyses indicate that children who were physically abused have a 54% increased odds of depressive disorders and a 92% increased odds of drug use.⁴⁴ Children experiencing emotional abuse or neglect can have even higher rates of psychological comorbidities (>300% increased odds of depressive disorders from emotional abuse and >200% increased odds from neglect, relative to children without abuse exposure).⁴⁴ Psychosocial outcomes in adulthood associated with past experiences of childhood violence may also include problems with finances, family, jobs, anger, and stress.⁴⁵

Lastly, violence is also associated with the development of major noncommunicable diseases, such as cardiovascular disease, cancer, chronic lung disease, and diabetes as well as key risk factors for several chronic diseases, including harmful alcohol use, tobacco use, physical inactivity, and obesity.^44,47 For example, data from meta-analyses, indicate that children who have experienced physical abuse have a 55% increased odds of tobacco smoking and a 32% increased odds of obesity, relative to nonabused children.⁴⁴ Although the relationship between childhood violence exposure and many noncommunicable diseases is still emerging, a growing number of prospective, longitudinal studies are establishing strong associations.

Violence prevention programs are often developed to address certain forms of violence (eg, child maltreatment, partner violence, youth violence) rather than multiple forms of violence. By focusing on those strategies that can reduce multiple forms of violence, practitioners have the potential to maximize gains in violence prevention. In Table 4 and Table 5, we highlight violence prevention strategies with some evidence for an effect on multiple forms of violence and that have been evaluated by major violence prevention evaluation bodies or possess other strong experimental evidence. The oldest and most tested violence prevention strategies are largely parent- and family-focused programs, early childhood education, therapeutic or counseling interventions, school-based programs, and public policy approaches.

Parent- and family-focused programs provide education and training to parents with the goal of improving emotional bonds between parents and children and teaching participants how to effectively discipline, monitor, and supervise children as well as strengthen access to social support and other resources. Programs for young children with components that teach parents communication skills and positive parent-child interaction skills and that include active role play and practice produce greater preventive effects than those without these components.⁶² Although parenting and family focused programs can vary substantially in content, method, and setting, a systematic review of early childhood home visitation programs detected a 38.9% reduction in episodes of child maltreatment in intervention participants compared with control participants.⁶³ The earlier parenting and family programs are delivered in a child’s life, the greater the benefits; however, significant benefits have also been demonstrated when delivered to adolescent populations.⁶⁴

The evidence also suggests that early childhood education can prevent future violence involvement. Early childhood education programs are associated with positive social and emotional development, lower rates of official reports of child abuse and neglect, less aggression and child behavior problems, and higher rates of secondary school completion and have also demonstrated long-term effects on violent and criminal behavior.^65,66 One example is the Chicago Child-Parent Center program, which provides a comprehensive educational program beginning in preschool, as well as other family support services to economically and educationally disadvantaged children.⁶⁷ A 15-year follow-up of preschool program participants across 25 sites in Chicago demonstrated statistically significant lower rates of juvenile arrests in the intervention vs control group (16.9% vs 25.1%, respectively).⁶⁷

There is also substantial evidence for therapeutic approaches and universal school-based violence prevention programs. Not only do therapeutic programs reduce the trauma-related harms of experiencing violence, but they also can prevent subsequent violence involvement. Cognitive behavioral therapy (CBT) and Multi-systemic therapy are 2 examples of therapeutic approaches. A Campbell Collaboration meta-analysis of CBT programs for criminal offenders demonstrated a crime recidivism reduction of 25% (recidivism rate of 0.30 in the intervention group compared with 0.40 in the control group over approximately 12 months after the intervention period).⁵³ As for universal school-based programs, such approaches are associated with a 15% relative reduction in violent behavior in students across all school years participating in these programs and a 29% reduction in violence among students in high school.⁶⁸ School-based programs have demonstrated reductions in both peer violence and teen dating violence and are also cost-effective.^48,69

Although many policy-level interventions for violence remain to be tested, there is some evidence for policies that aim to reduce alcohol-related harms. Given the strong association between alcohol use and violence involvement, reductions in alcohol consumption are expected to be associated with reduced levels of multiple forms of violence. Based on systematic reviews, the Community Preventive Services Task Force recommends increasing alcohol prices, limiting days and hours of sale, regulation of alcohol outlet density, upholding liability of establishments for alcohol-related harm committed by customers (dram shop liability), enhanced enforcement of laws prohibiting the sale of alcohol to minors, and screening and brief interventions for problem drinkers.⁴⁹

There are also other policy- and community-level approaches that represent promising strategies to prevent multiple forms of violence. Violence is higher in communities where there are limited economic opportunities; where there are high concentrations of poor and unemployed people; where people move frequently; and where there are limited public, mental health, and social services available to residents and fewer civic and voluntary associations.³¹ Consequently, the evidence for other policy- and community-level approaches to address these characteristics points to income-strengthening approaches (eg, subsidies or cash transfers), urban upgrading (eg, improved transportation, lighting, buildings, green space), economic development strategies (eg, business improvement districts), and residential mobility programs that enable families living in disadvantaged environments to resettle in more advantaged neighborhoods.^70–72 Increasing family income through subsidies or cash transfers, for example, has been shown to reduce child abuse and neglect, youth violence, and partner violence.^58,59,71

Lastly, bystander strategies are increasingly being used to prevent sexual violence, teen-dating violence, and bullying. With this approach, participants are trained to recognize potentially violent situations or behaviors that they see occurring and are taught skills to safely intervene. This approach also seeks to change underlying social norms that promote violence. A meta-analysis of bystander education to prevent sexual assault on college campuses found moderate effects on both bystander efficacy and intentions to help others at risk; smaller but significant effects were seen on increasing actual bystander helping behaviors, decreasing acceptance of rape myths, and decreasing rape proclivity.⁵⁶ Additionally, a recent meta-analysis of bullying programs detected an increase in bystander interventions among program recipients (an increase of 20% of 1standard deviation more than control group participants).⁵⁷

Although less is known about the modifiable factors that serve as protective buffers in the face of disadvantage, previous research suggests that connectedness and community-level collective efficacy are protective factors that may offset many of the negative influences in disadvantaged environments. These factors also seem to be protective across multiple forms of violence, including child maltreatment, youth violence, intimate partner violence, and suicidal behavior.⁷³ Although, to date, few interventions in these areas have been tested and evaluated, it is a promising area for future research. It is also important to acknowledge the significant contributions to violence prevention and response elucidated by other domains, such as criminology. Strategies such as problem-oriented policing are also associated with important effects on violence reduction. The science of violence prevention has made significant progress over the last 2 decades. Widespread dissemination and adoption of available evidence-based strategies, however, is still needed.

Many health care or clinical approaches to violence prevention are still early in development and, in general, there is limited experimental evidence for such approaches. However, a variety of strategies are being pursued and merit additional evaluation. Individuals exposed to violence can use health care services at a high rate and some clinicians have established programs designed to prevent their patients’ future involvement in violence and recidivism for violent injury (Box).^76,80 Such programs often are operated by emergency departments and trauma services^80,81; however, primary care clinics also have implemented programs to prevent violence, such as the Safe Environment for Every Kid (SEEK) model, a pediatric outpatient program. The SEEK program consists of identification of risk factors, offering brief counseling, and referring patients for services. A randomized clinical trial in which participants were followed up for more than 3.5 years found that children whose families were in the SEEK intervention had a significantly lower rate of official child protective services reports of child maltreatment (13.3%) than did those in the control group (19.2%). Intervention families also experienced improved health benefits such as lower rates of delayed immunizations.⁵⁴ In addition to the identification of risk factors for violence involvement, clinicians can be trained to recognize the signs and symptoms that may be associated with experiencing violence, such as injuries; unexplained chronic pain; gastrointestinal symptoms; genitourinary symptoms; repeated unintended pregnancies or sexually transmitted disease; symptoms of depression, anxiety, and sleep disorders; alcohol or other substance abuse⁸²; and behavioral problems in children.

New incentives and opportunities have been created to improve identification and assistance of patients at risk of violence and those presently experiencing violence. With the passage of the Affordable Care Act, screening adolescent and adult women for interpersonal violence and counseling must now be covered by many health plans with no cost sharing for patients.⁷⁵ Reimbursement rates and implementation details are likely to differ across plans, but this may facilitate identification of such patients and support on-going efforts. Large trials have shown little efficacy if the intervention for patients who screened positive for intimate partner violence involved providing them a resource list or informing their clinician with subsequent discussion and referral left to the discretion of the clinician.^83,84 Programs that have followed a positive screen result with more intensive support, such as a clinic-based CBT intervention, have noted improved outcomes.⁸⁵ One such program, which screened minority women at prenatal care clinics and then provided CBT, demonstrated a reduction in subsequent intimate partner violence (23.3% in intervention group vs 37.8% in control group overall follow-up interviews; intervention participants also gave birth to a lower proportion of infants with very preterm birth [1.5% vs 6.6%]).⁸⁵ More research is needed to better identify elements of programs that most effectively assist individuals found to be experiencing intimate partner violence or to identify other novel strategies. For example, medical-legal partnerships, an approach that attempts to better integrate legal services for patients into clinical care, can potentially assist clinicians with interventions not typically considered by the medical community. For example, in 1 retrospective cohort study, at the 12-months follow-up, women who had obtained permanent protection orders had a rate of police-reported physical abuse that was 20% of those women without protection orders (rate of 2.9 incidents per 100 person-years in intervention vs 14.0 incidents per 100 person-years in control).⁸⁶

Some health systems have also attempted to address underlying risk factors by various forms of community engagement. For example, hospital systems have funded school-based educational programs that attempt to modify early risk factors for violence.⁷⁶ Other health care systems have begun to intentionally purchase produce, goods, or services from local businesses in high-risk communities in an attempt address underlying economic risk factors for violence involvement.⁷⁶ These strategies represent early engagement of health care systems with more population-level preventive approaches; evaluation of such strategies is needed to best guide efforts.

The scientific literature indicates quite clearly that preventing interpersonal violence is strategic from a health and public health perspective. It is strategic because of the consistently documented high levels of violence to which young children, adolescents, and young adult women and men are exposed. Furthermore, exposure to violence plays an important role, not just in causing physical injuries and homicide, but also in the etiology of mental illness, chronic disease, and infectious diseases such as HIV. Thus, preventing exposure to violence can have downstream effects on a broad range of health problems. Finally, there is a substantial and rapidly growing evidence base on what works to prevent violence. This evidence suggests that priority should be given to interventions that can affect multiple forms of violence, particularly those that seek to prevent violence among children and youth. The effects of violence and the probability of involvement in future violence are dose dependent; thus, considerable gains can be made by early intervention.