Welte JW, Barnes GM, Tidwell MC, Hoffman JH. Research Institute on Addictions, State University of New York at Buffalo. Psychol Addict Behav. 2009 Mar;23(1):105-12.

A random telephone survey was conducted with 2,274 United States residents aged 14 to 21. Analyses were performed to assess the relationship between the specific gambling games played and the extent of problem gambling symptoms. The forms of gambling that were most associated with gambling problems were card games, casino gambling, “other” gambling on routine activities, and betting on games of skill such as basketball, pool, or golf. The form of gambling that made the largest contribution to gambling problems per 14 days of play was casino gambling. The hypothesis that rapid forms of gambling, such as slot machines, would be the most problematic forms of gambling was not upheld. (PsycINFO Database Record (c) 2009 APA, all rights reserved).