One of the best ways to introduce an article on the epidemiology of drug use and drug dependence is to ask some basic questions that epidemiologic studies can answer but laboratory and clinical studies cannot. Here are some examples:

In the late 1990s in the United States, about how many ages 12 to 17 had used cocaine at least once?

In the late 1990s, within which U.S. population subgroups were active cocaine users most likely to be found?

Within the United States in the early 1990s, among those aged 15 to 24 who had used cocaine, what proportion had become dependent on it?

In the early 1990s, which age group within the U.S. population was most likely to have experimented with cocaine, and which age group was most likely to have developed cocaine dependence?

For a young adult living in the United States, what...