1996 National Household Survey on Drug Abuse: Preliminary Results

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11. DISCUSSION OF RESULTS

The 1996 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 1996 NHSDA data show that overall drug use remains level and that the rate of drug use among youths may be leveling off as well, after several years of increase. However, there are indications of increasing use of hallucinogens among youths and increases in new heroin users who are smoking, snorting, or sniffing the drug. In addition, estimated rates of youth initiation of marijuana and other drug use were at historically high levels, and a significant increase in pastmonth illicit drug use among young adults age 18-25 years between 1994 and 1996 was observed.

The decrease in illicit drug use among youth is an important finding that should be interpreted with caution. It is not possible to determine if youth drug use will continue to decline, has leveled off, or will turn up again, based on only the 1996 data. Other evidence supports the finding that drug use has perhaps leveled off among youth. Indications of the leveling were reported in two other surveys of youth. The 1996 Monitoring the Future (MTF) study showed that while past month marijuana use among high school seniors increased from 11.9 percent in 1992 to 21.2 percent in 1995, the rate was 21.9 percent in 1996. 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, and 22 percent in 1996 (PDFA, 1997). Furthermore, both of these surveys, as well as the NHSDA, show a leveling (from 1995 to 1996) of perceived risk measures that had been declining prior to 1995.

The new NHSDA data on youth drug use are not, however, entirely consistent with the MTF data. The MTF showed continuing increases in past month use of any illicit drug among eighth graders (ages 13-14) and tenth graders (ages 15-16) in 1996. This is in contrast to the NHSDA data, which show decreases among youths 12-15 years old and no change among youths age 16-17 years old between 1995 and 1996. Further analysis of these data may help explain this discrepancy, but it is also important to recognize the methodological differences between the NHSDA and the MTF that could cause these discrepancies. For example, comparisons between MTF estimates for high school seniors and NHSDA estimates for older teenagers may be affected by the exclusion of school dropouts in the MTF, and comparisons between MTF estimates for eighth graders with NHSDA estimates for younger teenagers may be affected by youths’ greater reluctance to reveal illicit behavior in a household setting than in a classroom setting (Gfroerer, Wright, and Kopstein in press).

Although the possible leveling of youth drug use may be good news, it is important to recognize that the NHSDA results show increases in the rate of past month illicit drug use for young adults age 18-25, and young people are still initiating illicit drug use at high rates. The estimated annual number of new marijuana users increased from 1.4 million in 1991 to 2.4 million in 1994, and remained at 2.4 million in 1995. The rate of marijuana initiation among youths age 12-17 remains 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 treatmentfacilities (NIDA 1996b; Greenblatt, Gfroerer and Melnick 1995; Epstein and Gfroerer 1997). The limitations of the NHSDA for measuring these kinds of drug use behaviors have made it difficult to either refute or support these reports. However, the 1996 NHSDA data show an increasing rate of past month heroin use from 1993 to 1996, and an increasing rate of lifetime heroin smoking, snorting, or sniffing between 1994 and 1996. In 1995, an estimated 141,000 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 1995. 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 1996 was not statistically significant.

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 28 percent of users in 1996). 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 1995 it was 43 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 1995. Heroin-related emergency room visits have increased from 12,000 in 1979 to 77,000 in 1995 (SAMHSA 1996d, e).

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 cocaineusers 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. (Rhodes 1993).

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.