Violence is the use of physical force to cause harm to people, or non-human life, such as pain, injury, death, damage, or destruction.[1] Some definitions are somewhat broader, such as the World Health Organization's definition of violence as "the intentional use of physical force or power, threatened[2] or actual, against oneself, another person, or against a group or community, which either results in or has a high likelihood of resulting in injury, death, psychological harm, maldevelopment, or deprivation."[3]
Internationally, violence resulted in deaths of an estimated 1.28 million people in 2013, up from 1.13 million in 1990.[4] However, the global population grew by roughly 1.9 billion during those years, showing a dramatic reduction in violence per capita. Of the deaths in 2013, roughly 842,000 were attributed to self-harm (suicide), 405,000 to interpersonal violence (homicide), and 31,000 to collective violence (war) and legal intervention.[4] For each single death due to violence, there are dozens of hospitalizations, hundreds of emergency department visits, and thousands of doctors' appointments.[5] Furthermore, violence often has lifelong consequences for physical and mental health and social functioning and can slow economic and social development.
In 2013, of the estimated 405,000 deaths due to interpersonal violence globally, assault by firearm was the cause in 180,000 deaths, assault by sharp object was the cause in 114,000 deaths, and the remaining 110,000 deaths from other causes.[4]
Violence in many forms can be preventable. There is a strong relationship between levels of violence and modifiable factors in a country such as concentrated (regional) poverty, income and gender inequality, the harmful use of alcohol, and the absence of safe, stable, and nurturing relationships between children and parents. Strategies addressing the underlying causes of violence can be relatively effective in preventing violence, although mental and physical health and individual responses, personalities, etc. have always been decisive factors in the formation of these behaviors.[6]
Types

The World Health Organization divides violence into three broad categories:[3]
- self-directed violence
- interpersonal violence
- collective violence
This initial categorization differentiates between violence that a person inflicts upon themself, violence inflicted by another individual or by a small group of individuals, and violence inflicted by larger groups such as states, organized political groups, militia groups and terrorist organizations.
Alternatively, violence can primarily be classified as either instrumental or reactive / hostile.[7]
Self-directed
Self-directed violence is subdivided into suicidal behaviour and self-abuse. The former includes suicidal thoughts, attempted suicides—also called para suicide or deliberate self-injury in some countries—and suicide itself. Self-abuse, in contrast, includes acts such as self-mutilation.
Collective

Unlike the other two broad categories, the subcategories of collective violence suggest possible motives for violence committed by larger groups of individuals or by states. Collective violence that is committed to advance a particular social agenda includes, for example, crimes of hate committed by organized groups, terrorist acts and mob violence. Political violence includes war and related violent conflicts, state violence and similar acts carried out by armed groups. There may be multiple determinants of violence against civilians in such situations.[8] Economic violence includes attacks motivated by economic gain—such as attacks carried out with the purpose of disrupting economic activity, denying access to essential services, or creating economic division and fragmentation. Clearly, acts committed by domestic and subnational groups can have multiple motives.[9] Slow violence is a long-duration form of violence which is often invisible (at least to those not impacted by it), such as environmental degradation, pollution and climate change.[10]
Warfare

War is a state of prolonged violent large-scale conflict involving two or more groups of people, usually under the auspices of government. It is the most extreme form of collective violence.[11] War is fought as a means of resolving territorial and other conflicts, as war of aggression to conquer territory or loot resources, in national self-defence or liberation, or to suppress attempts of part of the nation to secede from it. There are also ideological, religious and revolutionary wars.[12]
Since the Industrial Revolution the lethality of modern warfare has grown. World War I casualties were over 40 million and World War II casualties were over 70 million.
Interpersonal
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Interpersonal violence is divided into two subcategories: Family and intimate partner violence—that is, violence largely between family members and intimate partners, usually, though not exclusively, taking place in the home. Community violence—violence between individuals who are unrelated, and who may or may not know each other, generally taking place outside the home. The former group includes forms of violence such as child abuse and child corporal punishment, intimate partner violence and abuse of the elderly. The latter includes youth violence, random acts of violence, rape or sexual assault by strangers, and violence in institutional settings such as schools, workplaces, prisons and nursing homes. When interpersonal violence occurs in families, its psychological consequences can affect parents, children, and their relationship in the short- and long-terms.[13]
Child maltreatment
Child maltreatment is the abuse and neglect that occurs to children under 18 years of age. It includes all types of physical and/or emotional ill-treatment, sexual abuse, neglect, negligence and commercial or other child exploitation, which results in actual or potential harm to the child's health, survival, development or dignity in the context of a relationship of responsibility, trust, or power. Exposure to intimate partner violence is also sometimes included as a form of child maltreatment.[14]
Child maltreatment is a global problem with serious lifelong consequences, which is, however, complex and difficult to study.[15]
There are no reliable global estimates for the prevalence of child maltreatment. Data for many countries, especially low- and middle-income countries, are lacking. Current estimates vary widely depending on the country and the method of research used. Approximately 20% of women and 5–10% of men report being sexually abused as children, while 25–50% of all children report being physically abused.[3][16]
Consequences of child maltreatment include impaired lifelong physical and mental health, and social and occupational functioning (e.g. school, job, and relationship difficulties). These can ultimately slow a country's economic and social development.[17][18] Preventing child maltreatment before it starts is possible and requires a multisectoral approach. Effective prevention programmes support parents and teach positive parenting skills. Ongoing care of children and families can reduce the risk of maltreatment reoccurring and can minimize its consequences.[19][20]
Youth
Following the World Health Organization, youth are defined as people between the ages of 10 and 29 years. Youth violence refers to violence occurring between youths, and includes acts that range from bullying and physical fighting, through more severe sexual and physical assault to homicide.[21][22]
Worldwide some 250,000 homicides occur among youth 10–29 years of age each year, which is 41% of the total number of homicides globally each year ("Global Burden of Disease", World Health Organization, 2008). For each young person killed, 20–40 more sustain injuries requiring hospital treatment.[21] Youth violence has a serious, often lifelong, impact on a person's psychological and social functioning. Youth violence greatly increases the costs of health, welfare and criminal justice services; reduces productivity; decreases the value of property; and generally undermines the fabric of society.[vague]
Prevention programmes shown to be effective or to have promise in reducing youth violence include life skills and social development programmes designed to help children and adolescents manage anger, resolve conflict, and develop the necessary social skills to solve problems; schools-based anti-bullying prevention programmes; and programmes to reduce access to alcohol, illegal drugs and guns.[23] Also, given significant neighbourhood effects on youth violence, interventions involving relocating families to less poor environments have shown promising results.[24] Similarly, urban renewal projects such as business improvement districts have shown a reduction in youth violence.[25]
Different types of youth on youth violence include witnessing or being involved in physical, emotional and sexual abuse (e.g. physical attacks, bullying, rape), and violent acts like gang shootings and robberies. According to researchers in 2018, "More than half of children and adolescents living in cities have experienced some form of community violence." The violence "can also all take place under one roof, or in a given community or neighborhood and can happen at the same time or at different stages of life."[26] Youth violence has immediate and long term adverse impact whether the individual was the recipient of the violence or a witness to it.[27]
Youth violence impacts individuals, their families, and society. Victims can have lifelong injuries which means ongoing doctor and hospital visits, the cost of which quickly add up. Since the victims of youth-on-youth violence may not be able to attend school or work because of their physical and/or mental injuries, it is often up to their family members to take care of them, including paying their daily living expenses and medical bills. Their caretakers may have to give up their jobs or work reduced hours to provide help to the victim of violence. This causes a further burden on society because the victim and maybe even their caretakers have to obtain government assistance to help pay their bills. Recent research has found that psychological trauma during childhood can change a child's brain. "Trauma is known to physically affect the brain and the body which causes anxiety, rage, and the ability to concentrate. They can also have problems remembering, trusting, and forming relationships."[28] Since the brain becomes used to violence it may stay continually in an alert state (similar to being stuck in the fight or flight mode). "Researchers claim that the youth who are exposed to violence may have emotional, social, and cognitive problems. They may have trouble controlling emotions, paying attention in school, withdraw from friends, or show signs of post-traumatic stress disorder".[26]
It is important for youth exposed to violence to understand how their bodies may react so they can take positive steps to counteract any possible short- and long-term negative effects (e.g., poor concentration, feelings of depression, heightened levels of anxiety). By taking immediate steps to mitigate the effects of the trauma they've experienced, negative repercussions can be reduced or eliminated. As an initial step, the youths need to understand why they may be feeling a certain way and to understand how the violence they have experienced may be causing negative feelings and making them behave differently. Pursuing a greater awareness of their feelings, perceptions, and negative emotions is the first step that should be taken as part of recovering from the trauma they have experienced. "Neuroscience research shows that the only way we can change the way we feel is by becoming aware of our inner experience and learning to befriend what is going on inside ourselves".[29]
Some of the ways to combat the adverse effects of exposure to youth violence would be to try various mindfulness and movement activities, deep breathing exercises and other actions that enable youths to release their pent up emotions. Using these techniques will teach body awareness, reduce anxiety and nervousness, and reduce feelings of anger and annoyance.[30]
Youth who have experienced violence benefit from having a close relationship with one or more people.[29] This is important because the trauma victims need to have people who are safe and trustworthy that they can relate and talk to about their horrible experiences. Some youth do not have adult figures at home or someone they can count on for guidance and comfort. Schools in bad neighborhoods where youth violence is prevalent should assign counselors to each student so that they receive regular guidance. In addition to counseling/therapy sessions and programs, it has been recommended that schools offer mentoring programs where students can interact with adults who can be a positive influence on them. Another way is to create more neighborhood programs to ensure that each child has a positive and stable place to go when school in not in session. Many children have benefited from formal organizations now which aim to help mentor and provide a safe environment for the youth especially those living in neighborhoods with higher rates of violence. This includes organizations such as Becoming a Man, CeaseFire Illinois, Chicago Area Project, Little Black Pearl, and Rainbow House".[31] These programs are designed to help give the youth a safe place to go, stop the violence from occurring, offering counseling and mentoring to help stop the cycle of violence. If the youth do not have a safe place to go after school hours they will likely get into trouble, receive poor grades, drop out of school and use drugs and alcohol. The gangs look for youth who do not have positive influences in their life and need protection. This is why these programs are so important for the youth to have a safe environment rather than resorting to the streets.[32]
Intimate partner

Population-level surveys based on reports from victims provide the most accurate estimates of the prevalence of intimate partner violence and sexual violence in non-conflict settings. A study conducted by WHO in 10 mainly developing countries[33] found that, among women aged 15 to 49 years, between 15% (Japan) and 70% (Ethiopia and Peru) of women reported physical and/or sexual violence by an intimate partner. A growing body of research on men and intimate partner violence focuses on men as both perpetrators and victims of violence, as well as on how to involve men and boys in anti-violence work.[34]
Intimate partner and sexual violence have serious short- and long-term physical, mental, sexual and reproductive health problems for victims and for their children, and lead to high social and economic costs. These include both fatal and non-fatal injuries