The study completed by Dr. Douglas Gentile at Iowa State University showed that 88% of American kids play video games and 8.5% of the kids who play video games show signs of addiction to gaming, similar to addictive gambling behavior.
Research at the University of Geneva on MMORPGs players showed that for certain individuals, involvement in MMORPGs can become problematic and engender tangible negative consequences in daily life. The results showed that problematic use of MMORPGs is associated with acting rashly in emotional contexts and motivation to be immersed in a virtual world.
The MMORPGs, like World of Warcraft, Age of Conan, Star Wars Galaxies, and EVE Online, are extremely addicting. Dr. Nick Yee gathered data from 3,000 MMORPGs players through online surveys and reported that there are three major types of motivations to play online: (1) achievement in the game; (2) social interaction, and (3) immersion in the virtual world. Dr. Yee’s study also showed that specific motivations to play online were associated with negative consequences resulting from online gaming.
 Gentile D. “Pathological Video-Game Use Among Youth Ages 8 to 18.” Psychol Sci. 2009 Jun;20(6):785.
 Billieux et al., “Psychological Predictors of Problematic Involvement in Massively Multiplayer Online Role-Playing Games: Illustration in a Sample of Male Cybercafé Players. Psychopathology 2011; 44:165-171.
 Yee N. “Motivations for play in online games.” Cyberpsychol Behav 2006; 9: 772–775.