There is a lot of work done in USA on Juvenile delinquency, gangs, street crimes, peer culture and sub-cultures. Also it depends what you mean by "violence" - in terms of committing an act, being part of an act, or an accomplice or a by stander  

Dear Morten,

Olweus is your famous researcher on this issue. TV and internet has contributed to this unacceptable behavior. Adult persons are also bullied in working places in Finland.

Some sources:

Challenging Violence in Schools: An Issue of Masculinities. Educating Boys, Learning Gender. Mills, Martin; ISBN: ISBN-0-335-20584-4

International Journal of Psychology and Psychological Therapy; Volume 8 Num. 1 - March 2008 - Pages 51-62. Bullying: Incidence of Peer Violence in the Schools of the Autonomous Community of the Basque Country

Maite Garaigordobil email: [email protected]

 Peer Violence Among Teenagers: Trends in Violence and Threats of Violence in Schools: 1991-2010

http://fcd-us.org/sites/default/files/Adolescent%20Violence.pdf

Findings

 Until 2010, more adolescents in middle and high schools were threatened than actually injured; these trends have now merged so that both threats and injuries occur at the same level.

 Trends in numbers of middle and high school students exposed to all four forms of violence began to increase in the 2002-2003 school year, peaked between 2007 and 2008, and began to decrease around 2008 and 2009.

 The annual numbers of adolescents injured intentionally without a weapon showed the greatest fluctuation. Injury without a weapon began to increase dramatically in 2003-2004, flattened out in 2008-2009, and went down slightly in 2009-2010.

 All four forms of violent bullying in schools show evidence of increases in the estimated numbers of middle and high school victims in the early 1990s – prior to the most recent peaks. It has been noted, however, that the 2002-2008 years were a period of increased access to the Internet and other forms of electronic communication and the creation and spread of social networking media.

The problem in making links is not being able to account for the actual variances in and of a factor - as they are both positive and negative messages in the media - but the issue is how and what explains the maintenance of these behaviors 

Como se sabe, a violência é muito difícil de ser conceituada, sua gênese infere estar nas relações interpessoais, sociais, políticas, e culturais. Ou seja, na vida de relação do ser humano consigo mesmo, com o outro e com o mundo. Crianças e adolescentes estão mais vulneráveis à violência. Dependendo de qual violência se está articulando, ela pode estar em todas as partes, nos hospitais, na escola, nas ruas, na própria residência, seja fazendo parte dela, no atuar ou no mantê-la, seja sendo cúmplice, reproduzindo a violência, ou ainda, guardando o silêncio, o que perpetua a manutenção desta violência. É importante não esquecermos que as crianças apreendem as informações que recebem do mundo e, ainda que não saibam o que estão fazendo, a reproduzem. E, de modo ímpar constroem sua cultura, compartilhando com seus pares este conjunto equilibrado de atividades cotidianas, agregando seus valores e interesses. Em relação às relações interpessoais entre escolas, alunos e pais, observa-se que as famílias, não raro, destituem-se da função educativa, entendendo que a função de educar cabe apenas à escola. Deste modo, parecem deixar de cumprir com suas responsabilidades junto ao seus filhos, às escolas e os alunos, e deixam de auxiliar na reflexão de medidas que possam sanar ou diminuir este problema com a violência entre seus pares. Para que seja prevenida, a violência precisa ser articulada na sociedade e nas redes de cuidados, em um movimento em conjunto na busca de compreender a dinâmica em que estes comportamentos violentos emergem e/ou estão inseridos, para que, atuando precocemente no âmbito dos problemas referente à violência possam ser avaliados e tratados. Sugestão de leitura: “We’re Friends, Right?”: Inside Kids’ Culture

William A. Corsaro,Department of Sociology -Indiana University- Bloomington, IN

USA. e Adolescence, youth and violence: identification, approach and management - Autores: Maria Helena Ruzany, Zilah Vieira Meirelles (2009)

Espero ter ajudado, boa sorte! Valéria Panhoni

Dear Valeria, thank you so much for your the post, I am very interested in reading what you have to say - I did the google translate but I think I am missing some words - are you able to also put an English version please - got the reference though

Here is a clumsy translation but it gives you the idea:

As we know, violence is very difficult to conceptualize, it is generated from interpersonal relationships, social, political, and cultural (contexts). That is, from the life of human relations with oneself, with others and with the world. Children and adolescents are more vulnerable to violence. Depending on which violence is articulated, it can be everywhere, in hospitals, in schools, on the streets, in their houses, as part of it, to act or maintain it, to reproduce violence, or by keeping silence, which perpetuates the maintenance of this violence. It is important to remember that children apprehend the information they receive from the world and yet do not know what they are doing, when reproducing it. And which is odd, they build their culture, share with peers this balanced set of daily activities, and add their values and interests. In relation to interpersonal relationships between schools, students and parents, it is observed that families, often, if deprived from the educational function, understand that the function of education fits just the school. Thus, thet seem to fail to comply with their responsibilities to their children, schools and students, and fail to assist in reflection on measures to remedy or alleviate the problem with violence among the peers. In order to be prevented, violence needs to be articulated in society and care networks, in cooperation in the search for understanding the dynamics how these violent behaviors emerge and / or are inserted, so that early acting on problem-related violence can be evaluated and treated. Suggested reading:

Dear Dr Ewalds-Kvist, thank you and excellent work. I do agree that violence as such is a difficult almost an abstract concept - I faced a similar challenge when we had to come with a definition for "animal cruelty" as part of CD and etc for clinicians - but what I am particularly interested in - what variable can be accounted a variance that is perhaps a good predictor of violence - I know each variable is quantified in different ways and socio-cultural definitions such as: crime, war, safety, survival and etc add another layer to understanding violence - thanks again though

The most cruical variable in my understanding in violence is lack of empathy;

the insight how it feels to be hurt. However, we have in our aggressive mice found a genetic component in aggression.

Would lack of empathy hold merit with regard to and holding and/or controlling for other  significant variables. We found in our study - that lack of impulsive control along with low SES also was associated with violence and delinquency

Yes, the genetic component in aggression can also be explained by flight and fright response