Researchers at the University of Missouri have authored a study
suggesting that MMORPGs are "the most addictive genre of video games." The study also indicates that unhealthy game play can manifest in both "very casual" and "hardcore" adult gamers, and it's usually fueled by desires for escapism, social interaction, and rewards.
"We did not find a perfect relationship between total time spent playing games and addictive video game behaviors," said study co-author Christopher Engelhardt, a postdoctoral research fellow in the Department of Health Psychology in the MU School of Health Professions. "Additionally, other variables such as the proportion of free time spent playing video games seem to better predict game addiction above and beyond the total amount of time spent playing video games."
The study says that MMORPGs pose a "triple threat" due to level advancement, team play, and enormous fantasy worlds that may "encourage pathological game use."