in the availability of legal gambling. The nature of the changes observed in those studies, however, was consistent with the view that increased opportunity to gamble results in more pathological and problem gambling.

In addition, a large majority of the statistically significant differences found in these studies were in the direction of increases in pathological and problem gambling. This pattern suggests that, during the recent decade, the prevalence of pathological and problem gambling has generally either stayed constant or increased. Further support comes from comparisons made by Volberg (1996a) and in the Shaffer et al. (1997) meta-analysis. Both observed that the results of state-level prevalence studies conducted in more recent years have shown higher prevalence rates than those conducted in the 1980s.

Vulnerable Populations

Several populations are of particular interest because of the possibility that they may be especially likely to develop gambling problems or, if such problems develop, because they may be especially vulnerable to their harmful effects. Other populations are of interest because the relative prevalence of pathological and problem gamblers among them may shed light on the risk factors and causes of pathological gambling. Among the populations of particular interest for one or the other of these reasons are adolescents, the elderly, men, minorities, and the poor. There are substantial numbers of studies of adolescent prevalence, but the research on other possible vulnerable populations is more limited. The discussion below first reviews the studies of adolescent problem gambling and then examines what little has been identified that bears on the other populations of interest.

Adolescents

Table 3-7 provides descriptive information on the studies compiled by Shaffer et al. (1997) that report on pathological or problem gambling among U.S. adolescents. Table 3-8 summarizes the available data on the percentage of gambling behavior among adolescents assessed over the full history of their experi-



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