Not all adolescent and young adult subgroups in society are at equal risk of being a recently active drug user (Johnston et al., 2002a; Wallace et al., 2003). During adolescence, at least, African-American youngsters have substantially lower prevalence of use of the full range of legal and illegal substances than their white, Hispanic, or Native American counterparts, although there seems to be some reversal of this difference in early and later adulthood (SAMHSA, 2002a). Native Americans tend to have the highest prevalence of use, and in early adolescence, Hispanic youth tend to have the next highest. Adolescent boys are somewhat more likely than girls to use most drugs, and quite a bit more likely to use them frequently. Van Etten, Anthony, and colleagues have pursued a line of research that traces the basic male–female difference in drug experience back to an earlier male excess in the experience of the first chance to try drugs; that

is, males have the chance to try illegal drugs earlier than girls and at any given age are more likely to have experienced a chance to try these drugs. However, once the first chance to try a drug is presented, girls are just as likely as boys to actually consume the drug (e.g., see Van Etten & Anthony, 2001; Van Etten, Neumarks, & Anthony, 1999). Contrary to popular opinion, rural areas now generally do not have lower prevalence of most types of drug use than more urban areas, and sometimes actually have higher rates, which speaks to how thoroughly the drug epidemic has diffused to all parts of American society. The finding that most forms of drug use do not vary much as a function of the educational level of the parents, a measure of socioeconomic status, also reflects this diffusion. The use of certain drugs does tend to concentrate in particular regions of the country—crystal methamphetamine use in the West, for example—but for the most part regional similarities are more noteworthy than the differences. Sometimes, when a new drug is coming onto the scene, such as crack in the 1980s and ecstasy in the late 1990s, there are larger geographic differences until the diffusion process takes place. Most of the demographic and family background subgroup differences mentioned above tend to enlarge during periods of greater use of a drug and to diminish during periods of contraction in use; but still they tend to remain consistent as to direction over long historical periods, with very few exceptions. Regional differences in cocaine use expanded dramatically in the early 1980s, at the height of the cocaine epidemic, with the West and the Northeast United States attaining considerably higher prevalence of use than the South or the North Central. But during the contraction period that followed, beginning in 1997, the West and Northeast also showed the most dramatic declines (Johnston, et al., 2003b).

The American drug epidemic of the 1960s and 1970s spread around the globe, as a mobile generation of young people traveled the world. Even so, illegal drug use generally did not penetrate so deeply into youth populations of other countries. A recent 30-country prevalence survey of illegal drug use among 15-year-olds (mostly in European countries) shows generally larger values for American adolescents than for any of the 30 other countries (Hibell et al., 2000). Despite the long-ago passing of forces giving special impetus to the American epidemic, and despite progress in prevention, we still are in the top rank.

A caution is in order, however. When an epidemic has occurred, as happened with cocaine in the 1970s and early 1980s, it can give rise to a considerable population of continuing, dependent users. A result is that “casualty” counts of impaired users needing treatment can lag behind general trends in prevalence of use.