tion in 1994 by age and other demographic characteristics (SAMHSA, 1995c).4 There are relatively large variations in the prevalence of illicit drug use by age group and by gender. The 18-25 age group is distinctly higher than other age groups, with the group 35 and older being lowest. Males are almost twice as likely as females to have used an illicit drug in the past month. Among other characteristics there are relatively small variations, with the exception that unemployed persons tend to have higher rates of drug use. There is relatively little variation in use rates by population density, indicating that illicit drug use has permeated the society and is not confined to certain areas.
One of the more interesting findings from this study and other population-based epidemiological studies is that African Americans under 25 tend to report rates of drug use that are similar to or lower than those of other racial or ethnic groups. This finding is not consistent with the impressions that many Americans have about rates of drug use, although a number of investigations have supported these findings (Bachman et al., 1991; Anthony et al., 1994; Wallace and Bachman, 1994). However, this may not be generally true for African Americans over 25, who tend to have higher rates of some illicit drug use than other racial or ethnic groups (Table 4.2).
Trends in the percentage of positive responses provide an indication of changes in the prevalence of use. As shown in Figure 4.1 for four age groups, the percentage of those who used any illicit drug in the previous month declined steadily from 1979 to 1991 in all age groups except the over-35 group, which consistently reported very low rates of illicit drug use in the past 30 days. In 1979, approximately 14 percent of the total household population reported having used one or more illicit drugs in the past month, compared with 6 percent in 1994 (SAMHSA, 1995c). The decreases were particularly dramatic among those aged 18 to 25, the age group that has historically had the highest rates of use. The decreases were more rapid in the earlier part of this period and have since leveled off, particularly in the two younger age groups. The most recent survey, conducted in 1994, however, shows a significant increase among the youngest respondents (ages 12-17) (SAMHSA, 1995c).
The MTF is a series of surveys funded by NIDA that examines the use of alcohol, tobacco, and illicit drugs among young people from grade 8 through age 32. The core of the study, which began in 1975, consists of