Long

Background. The mobile game market has been rapidly growing worldwide, especially in Japan. Because mobile games often use a free-to-play business model that involves additional in-game purchases, some monetary and event mechanics of mobile games have been controversial in Japan. Purpose. This study explored the long-term effects of monetary and event features of game mechanics on pathological gaming, weekly exposure and monthly expenditure among teenagers and young adults in Japan. Method. A total of 948 teenagers and young adults participated two surveys in November 2013 and in May 2014. Pathological gaming, weekly game exposure, monthly expenditure and preference for gambling were measured. The participants listed up to three games they played, and their monetary and event mechanics were analysed using content analysis. The degrees of exposure to each mechanics were calculated by combining the content analysis with a longitudinal study. Results. Players who were exposed to a higher amount of limited-time only gacha, a virtual lottery machine, were likely to spend more money six months later. However, players who were exposed to a lower amount of normal gacha were likely to spend more money later among players who preferred gambling. No monetary effects on pathological gaming per se were found. Conclusion. This study shows that some game mechanics can cause excessive use of time and money for certain players