How to cite:  Anderson, C. A., Sakamoto, A., Gentile, D. A., Ihori, N., & Shibuya, A., Yukawa, S., Naito, M., & Kobayashi, K. (2008).  Longitudinal effects of violent video games on aggression in Japan and the United States.  Pediatrics, 122, e1067-1072.
 

Context: Youth worldwide play violent video games many hours per week. Prior research suggests that such exposure can increase physical aggression.
Objective: To determine whether high exposure to violent video games increases physical aggression over time in both high (U.S.) and low (Japan) violence cultures. We hypothesized that amount of exposure to violent video games early in a school year would predict changes in physical aggressiveness assessed later in the school year, even after statistically controlling for sex and prior physical aggressiveness.
Design: In three independent longitudinal samples, participants' video game habits and physically aggressive behavior tendencies were assessed at two points in time, separated by three to six months.
Participants: Three population-based samples were assessed. One sample consisted of 181 Japanese junior high students ranging in age from 12 to 15 years. A second Japanese sample consisted of 1050 students ranging in age from 13 to 18 years. The third sample consisted of 364 U.S. 3rd, 4th, and 5th graders ranging in age from 9 to 12 years.
Results: Habitual violent video game play early in the school year predicted later aggression even after controlling for sex and prior aggressiveness in each sample, ps < .01. Those who played a lot of violent video games became relatively more physically aggressive. Multi-sample structure equation modeling revealed that this longitudinal effect was of a similar magnitude in the U.S. and Japan for similar age youth (Bs = .158 & .139, respectively, ps < .0001), and was smaller (but still significant) in sample that included older youth (B = .075, p < .01).
Conclusions: These longitudinal results confirm earlier experimental and cross-sectional studies that had suggested that playing violent video games is a significant risk factor for later physically aggressive behavior, and that this violent video game effect on youth generalizes across very different cultures. As a whole, the research strongly suggests reducing the exposure of youths to this risk factor.
 
 
Studies funded in part by: The Laura Jane Musser Fund; Centers for Disease Control and Prevention; The Broadcasting Policy Division in the Information & Communications Policy Bureau, Ministry of Public Management, Home Affairs, Posts, and Telecommunications, Japan

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