1997 National Household Survey on Drug Abuse:  Preliminary Results

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12. DISCUSSION OF RESULTS

The 1997 National Household Survey on Drug Abuse provides a comprehensive description of substance use and abuse in the United States. The survey provides reliable information to assess trends, patterns, and relationships associated with substance abuse. Given the difficulties involved in collecting data on illegal and sensitive behaviors, the interpretation of the NHSDA data is best made in conjunction with other available data sources, taking into account the strengths and limitations of each source.

The 1997 NHSDA data show that overall drug use remained level, but the rate of drug use among youths continued to increase in 1997. In addition, there are indications of increasing use of heroin involving new users who are smoking, snorting, or sniffing the drug. Estimated rates of youth initiation of marijuana and other drug use were at historically high levels.

Comparisons of the NHSDA results for youth marijuana use with results from other surveys show that the trends during the 1990s are generally consistent across these surveys. The NHSDA showed substantial increases in past month use among youths age 12-17 from 1992 to 1995 (from 3.4 percent to 8.2 percent), then rates of 7.1 percent in 1996 and 9.4 percent in 1997. The Monitoring the Future (MTF) study showed that past month marijuana use among high school seniors increased from 11.9 percent in 1992 to 21.2 percent in 1995. The rate did not change significantly in 1996 (21.9 percent) and then was estimated at 23.7 percent in 1997 (not a statistically significant increase). The Partnership Attitude Tracking Study (PATS), a nationally representative survey of students sponsored by the Partnership for a Drug-Free America, estimated rates of past month marijuana use for students in grades 7-12 to be 14 percent in 1993, 21 percent in 1995, 22 percent in 1996, and 23 percent in 1997 (PDFA, 1998). Furthermore, both of these surveys, as well as the NHSDA, show generally declining trends (from 1995 to 1997) of marijuana perceived risk measures from 1995 to 1997, continuing a pattern that emerged in both MTF and NHSDA around 1991.

The NHSDA data on youth drug use are not, however, entirely consistent with the MTF and PATS data when specific year to year variations and trends among subgroups of youth are examined. Further analysis of these data may help explain these differences, but it is also important to recognize the methodological differences between the NHSDA and the MTF and PATS that could be the cause. Differences in populations covered, time periods of data collection, questionnaire wording, effects of nonresponse bias, and interview setting (school vs, home) could affect the resulting estimates, both in terms of levels and trends (Gfroerer, Wright, and Kopstein 1997).

The estimated annual number of new marijuana users increased from 1.4 million in 1991 to 2.4 million in 1994, and remained at about the same level in 1995 and in 1996. The rate of marijuana initiation among youths age 12-17 is at its highest level ever. This has important implications for substance abuse prevention and treatment efforts. In terms of prevention, there is an obvious need to focus immediate attention on children and adolescents. In the long run, the expanding pool of young people using illicit drugs will probably result in continuing pressure on the substance abuse treatment system in future years, as many new drug users progress to addiction and require intervention.

Reports of increasing heroin and methamphetamine abuse have been prominent over the past few years, based on data from medical examiners, emergency departments, and drug treatment facilities (NIDA 1996; SAMHSA 1998c). The limitations of the NHSDA formeasuring these kinds of drug use behaviors have made it difficult to either refute or support these reports.

However, the NHSDA data show an increasing rate of past month heroin use from 1993 to 1997, and an increasing rate of lifetime heroin smoking, snorting, or sniffing between 1994 and 1997. In 1996, an estimated 171,000 people used heroin for the first time. Rates of initiation have increased for both youths age 12-17 and for young adults age 18-25 between 1990 and 1996. Most new heroin users in recent years were under age 26 and were smoking, snorting, or sniffing heroin. Methamphetamine use (lifetime) rates also suggest some increase, although the change between 1994 and 1997 was not statistically significant. There was a statistically significant increase in lifetime methamphetamine use among youths age 12-17 from 1996 to 1997.

The NHSDA continues to show the aging of the drug using population. Cohorts who were teenagers and young adults in the 1960s and 1970s are now older, and although most no longer use illicit drugs, many still do. This aging cohort, composed primarily of the baby boom, is adding increasingly to the "35 and older" age group shown in NHSDA reports. Thus, the proportion of drug users that are age 35 and older continues to increase (from 10 percent of users in 1979 to 29 percent of users in 1997). Data from the Drug Abuse Warning Network (DAWN) on drug-related hospital emergency department episodes also show the impact of the aging cohort of drug users. In 1979, 12 percent of patients with cocaine episodes were age 35 or older. By 1985 the proportion was 19 percent, and by 1996 it was 45 percent.

Many of the drug users in this aging cohort have used drugs for many years and have developed severe drug problems. This may partly explain the continuing rise in hospital emergency department episodes, which are more likely to involve these heavy users than occasional users or those who use only marijuana. Cocaine-related emergency room visits have increased from 5,000 in 1981 to 29,000 in 1985 (the peak year for past month cocaine prevalence in the NHSDA) to 144,000 in 1996. Heroin-related emergency room visits have increased from 12,000 in 1979 to 70,500 in 1996 (SAMHSA 1996d, 1997b).

It is important to recognize the limitations of both DAWN and the NHSDA for measuring the prevalence of heavy drug use. As is discussed in DAWN reports, there are many factors that could influence trends in drug-related episodes. These factors include changes in the purity and availability of drugs, changes in patterns of use (e.g., drug combinations or route of administration), availability of treatment programs ("seeking detoxification" was the reported reason for visit in 25 percent of cocaine-related episodes in 1995), and changes in patient management practices. Furthermore, research has indicated that only a small, nonrepresentative proportion of heavy cocaine users account for cocaine-related emergency room episodes (Gfroerer and Brodsky 1993).

Sample size, coverage, and validity problems are likely to be more pronounced for NHSDA estimates of heavy users than for other measures generated by the survey. Therefore, estimates of heavy use are considered conservative, and changes over time are generally not statistically significant. For example, the NHSDA has produced estimates of about 600,000 frequent cocaine users with no significant changes in the size of this population since 1985. By using various other data sources and making a number of assumptions (many of which are of uncertain validity), researchers have estimated that there are over 2 million frequent cocaine users in the U.S. (ONDCP 1998).

Clearly there is considerable uncertainty about the size of the heavy drug-using population. Estimates from the NHSDA can provide useful data to help describe this population, but should only be used in conjunction with other data sources. Appendix 2, Section IV (Estimation of Heavy Drug Use) contains a discussion of a methodology developed by OAS that uses arrest and treatment data to adjust NHSDA estimates of heavy drug use.

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This page was last updated on February 05, 2009.