Scott, D. (1995). The effect of video games on feelings of aggression. Journal of Psychology: Interdisciplinary and Applied, 129 (2), 121-132.

Abstract:  Explored some inconsistencies in the empirical research which suggests that playing arcade/computer games increases aggressiveness. Aggressiveness was manipulated as the independent variable. As dependent variables, the Buss-Durkee Hostility-Guilt Inventory and the Eysenck Personality Questionnaire (EPQ) were administered to 117 undergraduates before and after they played 1 video game. There was no linear pattern in aggressive affect change across 3 games that contained varying levels of violence. The general pattern was that the moderately aggressive game substantially decreased feelings of aggressiveness, while the highly aggressive game resulted in much less of an increase in aggressiveness than had been hypothesized, although no more so than occurred in the control game. (PsycINFO Database Record (c) 2004 APA, all rights reserved)