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Risk and Protective Factors for Adolescent Drug Use:
Findings from the 1999 National Household Survey on Drug Abuse

Appendix C: Distribution of Risk and Protective Factors and Substance Use, by Age and Gender

C.1 Substance Use, by Age and Gender

When examining any set of risk and protective factors relative to adolescent substance use, it is important to begin with an understanding of the ways in which substance use and other activities and relationships change with age. As mentioned in Chapter 2, behavior, especially substance-using behavior, can change rapidly during adolescence, and it can be potentially misleading to treat 12 to 17 year olds as an undifferentiated age group without closer inspection. The youth sample represented in the 1999 National Household Survey on Drug Abuse (NHSDA) can be thought of as six consecutive 1–year age groups.33 Figure C.1 shows the association between age and substance use, separately for males and females, for three kinds of substances (i.e., cigarettes, alcohol, and marijuana) showing two distinct measures for each substance, namely, whether it was ever used during an individual's lifetime and during the past year. These calendrical categories are not exclusive: A person who used during the past year is included in the ever-used group.

According to the 1999 NHSDA, an estimated 13 percent of males and 9 percent of females who were 12 years old in 1999 had ever smoked a cigarette. But for those aged 17, these figures were about 59 percent for males and 57 percent for females. Although not shown, the percentage of youths who smoked within the past month, although much lower at every age, showed a very similar pattern, rising from about 2.1 percent at age 12 to about 28.7 percent at age 17, with only slight differences between males and females. The same pattern of steady increase with age and minimal differences between males and females was characteristic of alcohol use and marijuana use. Alcohol was used by the highest percentage of youths, closely trailed by cigarettes (with a somewhat flatter age distribution). The differences in the prevalence rates of these substances varied by year of age; for example, 12 year olds were approximately 5 times more likely to have used alcohol in the past year (7.4 percent) than to have used marijuana (1.5 percent), but among 17 year olds the rate of past year alcohol use (58 percent) was only twice as high as the rate of past year marijuana use (27 percent).

Figure C.1 Prevalence of Lifetime and Past Year Substance Use in the U.S. Civilian, Noninstitutionalized Population Aged 12 to 17, by Age and Gender: 1999

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Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999.

This pattern of steadily increasing drug use at each age, with relatively small if any differences between males and females, was common to youths who were white, black, or Hispanic, as well as youths in the "other" category. White youths reported higher rates of cigarette smoking than other racial/ethnic groups, and black youths reported generally lower prevalence of alcohol use (see Table 3.1 in Chapter 3). White and Hispanic youths also reported higher rates of past year marijuana use than blacks or youths in the "other" category.

C.2 Risk and Protective Factors: Variation by Age

As is the case with the prevalence of substance use, the distributions of risk and protective factors also vary by age. As an illustrative example, Figure C.2 displays the percentage of youths who reported that they would strongly disapprove if a same-aged youth were to try marijuana once or twice, smoke one or more packs of cigarettes a day, or have one or two drinks of an alcoholic beverage nearly every day. The percentage of youths who would strongly disapprove of same-aged youths using these substances was notably higher among 12 year olds (86 percent for trying marijuana, 82 percent for daily smoking, and 83 percent for daily alcohol use) than for 17 year olds (48 percent for trying marijuana, 54 percent for daily smoking, and 53 percent for daily alcohol use). Youths aged 12 or 13 were more likely to strongly disapprove of trying marijuana once or twice than of daily cigarette smoking or alcohol use, but this pattern was reversed among youths aged 16 or 17. Many other risk and protective factors, particularly factors specific to substance use (e.g., community norms toward youth substance use, parental attitudes toward youth substance use, friends' use of substances, prevalence of substance use in school) showed similar patterns of gradual change for each age group.

Figure C.2 Percentages of Youths Aged 12 to 17 Reporting Strong Disapproval of Same-Aged Youths Using Marijuana, Cigarettes, and Alcohol, by Age: 1999

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Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999.

The associations between risk and protective factors and youth substance use also can vary by age. The association between youth marijuana use and attending a special alcohol/drug education course taught by someone other than a regular teacher serves as an example. In 1997, 38 percent of youths aged 12 to 17 who had been enrolled in school had attended a special alcohol/drug education course taught by someone other than a regular teacher in the past year. Youths who had taken such a course were less likely to have used marijuana in the past year (11 percent) than those who had not taken one (19 percent). Therefore, one might conclude that attending these special courses was associated with a reduction in the prevalence of marijuana use among youths aged 12 to 17. However, looking at the results by single year of age, the special courses may be effective for ages 12 to 15, but not for ages 16 and 17 (Figure C.3). One possible reason for this is that special courses designed for younger youths may be aimed at prevention of substance use among nonusers, whereas special courses designed for older youths may be aimed to treatment among youths who already have initiated use.

Figure C.3 Percentage of Youths Reporting Past Year Marijuana Use, by Age and by Whether or Not Youths Had a Special Course on Drug Education Taught by a Special Teacher: 1997

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Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1997.

Because of these differences between ages in the risk and protective factors and in the prevalence of substance use, age was included as a covariate in the prediction models presented in Chapter 4 of this report. By including age as a covariate, these models adjust for the differences between age groups in the risk and protective factors and the prevalence of substance use.

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This page was last updated on July 17, 2008.