Hopf, W., Huber, G., & Weiß, R. (2008). Media violence and youth violence: A 2-year longitudinal study. Journal of Media Psychology: Theories, Methods, and Applications, 20(3), 79-96. Retrieved June 24, 2009, doi:10.1027/1864-1105.20.3.79

The frequency of exposure to media violence and eight additional risk factors were path-analyzed in a 2-year longitudinal study. The exposure to media violence (total score) affected students’ later violence (β = .28) and later violent delinquency (β = .30) more strongly than other risk factors. Direct effects were also caused by risk factors assessed at Time 1, which in turn were reinforced by the remaining risk factors on the second or third stratum of analysis. Of particular importance are the findings that (1) playing violent electronic games is the strongest risk factor of violent criminality and (2) both media-stimulated and real experiences of aggressive emotions associated with the motive of revenge are core risk factors of violence in school and violent criminality. The results of our study show that the more frequently children view horror and violence films during childhood and the more frequently they play violent electronic games at the beginning of adolescence the higher will these students’ violence and delinquency be at the age of 14. (PsycINFO Database Record (c) 2008 APA, all rights reserved)(from the journal abstract)