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Misuse of Prescription Drugs |
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This chapter presents information on initiation of nonmedical use of prescription-type psychotherapeutic drugs. Measures of drug use initiation, also known as incidence or first-time use, are important for policymakers and researchers because they often serve as leading indicators of emerging patterns of substance use. This information also can aid in assessing the effectiveness of current prevention programs and determining where future prevention efforts need to focus.
Estimates are presented for the numbers of new nonmedical users of prescription-type psychotherapeutic drugs, the rates of initial use among persons at risk, and the age at first use among new users. Differentials and trends in incidence estimates are considered for pain relievers, tranquilizers, stimulants, and sedatives; patterns for OxyContin® and methamphetamine are examined within their respective therapeutic classes.
With its large sample size and oversampling of youths aged 12 to 17 and young adults aged 18 to 25, the National Survey on Drug Use and Health (NSDUH) provides a variety of estimates related to substance use initiation. Lifetime users are asked to report the age they first used a given drug, and persons who initiated use at or 1 year prior to their current age are asked to report the year and month that they first used. This information, along with the interview date and the respondent's date of birth, is used to determine a date of first use for each substance used by the respondent. Estimates of the number of initiates, rates of initiation, and average age at first use can be constructed for specific time periods. For example, estimates for calendar years from 1965 to 2003 are tabulated, based on combined 2002-2004 NSDUH data, to show long-term trends in initiation. Tables showing these trends are available on request from OAS or through the Internet at http://oas.samhsa.gov/WebOnly.htm.
However, recent methodological assessments of these long-term trend estimates based on calendar year of initiation suggest that these estimates are biased due to suspected recall errors that seem to increase with the length of recall (Gfroerer, Hughes, Chromy, Heller, & Packer, 2004). Evidence of telescoping, where respondents shift their reported age at first use either closer to their current age or further from the interview date, also has been found (Golub, Johnson, & Labouvie, 2000; Johnson & Schultz, 2005).
In response to this problem, the 2004 NSDUH national findings report (Office of Applied Studies [OAS], 2005b) introduced a new approach in NSDUH for studying substance use initiation based on information on first use within the 12 months prior to the survey interview. Estimates for each year are produced independently based on the data from the 2002, 2003, and 2004 surveys. With the survey data having been collected continuously throughout the respective years, initiation in the prior 12 months would have occurred in the previous calendar year in many of the cases.
Most of the estimates of past year initiation reported in this chapter have been averaged over the three surveys to obtain larger sample sizes and greater precision. It should be noted that when data on past year initiation are disaggregated by age at the time of the survey, a portion of the initiates actually have begun using the drug when they were a year younger than when surveyed. Thus, for youths aged 12 to 17 at the time of the survey, initiation may have occurred at age 11 for some of the 12 year olds. It also should be noted that these estimates do not include initiation at age 17 by youths who had reached age 18 at the time of the interview. See the 2004 NSDUH summary report (OAS, 2005b) for further discussion of methods and possible bias in initiation estimates.
The statistics reported in this chapter include (a) estimated numbers of initiates1; (b) average age at first use of persons who initiated use in the 12 months prior to the survey; (c) percentages of initiates relative to the population within their specific group; (d) percentages of initiates relative to persons at risk of initiation (i.e., those who previously have never used the drug); and (e) percentages of initiates among past year users. For the calculation of the initiation rates relative to persons at risk, the denominators include persons who have either never used the drug up to the time of the survey and those who initiated use within the specified time period (e.g., within the 12 months prior to the survey). The percentage of past year initiates among past year users is an indicator of the extent to which recent users of the particular drug are new to use of the drug or had used previously; with many lifetime users not using in the past year (i.e., presumably having discontinued use), the percentage of past year initiates among past year users reflects the complement of discontinuation. The average age of new initiates is a dynamic measure of the age profile of persons just beginning to use particular drugs in a specific timeframe.
Using these measures, this chapter presents three types of information on initiation of nonmedical use of prescription-type psychotherapeutic drugs: (a) trends in past year initiation from 2002 to 2004; (b) numbers, incidence rates, and mean ages of past year initiates averaged for 2002, 2003, and 2004 based on data collected in those years; and (c) long-term trends in incidence by calendar year based on the methodology employed in reports from the 1999 to 2003 NSDUHs. For the latter, readers are reminded of the limitations described previously.
Among persons aged 12 or older, there were no statistically significant changes between 2002 and 2004 in the numbers of initiates or the rate of initiation for any prescription-type psychotherapeutic drug or for the separate therapeutic classes (Table 4-A). In 2004, 1.5 percent of persons aged 12 or older who were at risk for initiation first used any prescription psychotherapeutic drug in the past 12 months.
| Percentage of Past Year Initiates among Persons at Risk for Initiation1,2 |
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|---|---|---|---|
| 2002 | 2003 | 2004 | |
| Drug | Aged 12 or Older | ||
| a Difference between estimate and 2004 estimate is statistically significant at the 0.05 level. b Difference between estimate and 2004 estimate is statistically significant at the 0.01 level. c Difference between estimate and 2003 estimate is statistically significant at the 0.05 level. d Difference between estimate and 2003 estimate is statistically significant at the 0.01 level. 1 Past Year Initiates are defined as persons who used the substance(s) for the first time in the 12 months prior to the date of the interview. 2 At Risk for Initiation is defined as persons who had not used the substance(s) in their lifetime or used the substance(s) for the first time in the past year. 3 Nonmedical use of prescription-type pain relievers, tranquilizers, stimulants, or sedatives; does not include over-the-counter drugs. Source: SAMHSA, Office of Applied Studies, National Survey on Drug Use and Health, 2002, 2003, and 2004. |
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| Nonmedical Use of Psychotherapeutics3 | 1.3 | 1.3 | 1.5 |
| Pain Relievers | 1.1 | 1.2 | 1.1 |
| Tranquilizers | 0.5 | 0.5 | 0.5 |
| Stimulants | 0.4 | 0.3 | 0.4 |
| Methamphetamine | 0.1 | 0.1 | 0.1 |
| Sedatives | 0.1 | 0.1 | 0.1 |
| Aged 12 to 17 | |||
| Nonmedical Use of Psychotherapeutics3 | 4.4 | 4.0 | 4.3 |
| Pain Relievers | 4.0 | 3.9 | 3.9 |
| Tranquilizers | 1.3 | 1.3 | 1.3 |
| Stimulants | 1.4a | 1.2 | 1.1 |
| Methamphetamine | 0.5 | 0.4 | 0.4 |
| Sedatives | 0.3 | 0.3 | 0.3 |
| Aged 18 to 25 | |||
| Nonmedical Use of Psychotherapeutics3 | 4.0 | 4.1 | 4.0 |
| Pain Relievers | 3.5 | 3.7 | 3.3 |
| Tranquilizers | 1.5 | 1.6 | 1.5 |
| Stimulants | 1.2d | 0.8b | 1.2 |
| Methamphetamine | 0.4 | 0.3a | 0.5 |
| Sedatives | 0.2 | 0.1 | 0.2 |
| Aged 26 or Older | |||
| Nonmedical Use of Psychotherapeutics3 | 0.4a | 0.5 | 0.6 |
| Pain Relievers | 0.3 | 0.4 | 0.4 |
| Tranquilizers | 0.3 | 0.2 | 0.3 |
| Stimulants | 0.1 | 0.1 | 0.1 |
| Methamphetamine | 0.0 | 0.0 | 0.0 |
| Sedatives | 0.1 | 0.1 | 0.1 |
Within age groups, there were some small but statistically significant changes. The rate of past year initiation of stimulant misuse among persons at risk for initiation (i.e., persons who had not previously misused any drug of this type) decreased from 1.4 percent in 2002 to 1.1 percent in 2004 for youths aged 12 to 17; among young adults aged 18 to 25, initiation of stimulant misuse declined from 1.2 percent in 2002 to 0.8 percent in 2003, but then increased in 2004 to its earlier rate of 1.2 percent. Among adults aged 26 or older, misuse of any prescription-type psychotherapeutic drug increased from 0.4 percent in 2002 to 0.6 percent in 2004.
From 2002 to 2004, an annual average of 2.7 million persons currently aged 12 or older initiated nonmedical use of any prescription-type pain reliever, tranquilizer, stimulant, or sedative in the 12 months prior to the survey (Table 4.1B). This constitutes 1.4 percent of the persons at risk of such initiation. The annual average number of new nonmedical users of pain relievers (2.4 million) exceeded the number of new users of marijuana (2.1 million) (Figure 4.1). There were an estimated 1.1 million new users of tranquilizers on average, comparable with the 1.0 million estimated cocaine initiates. New stimulant users numbered 764,000, and new sedative users 214,000. Among specific prescription drugs, an annual average of 292,000 persons used methamphetamine for the first time. Past year OxyContin® initiates were estimated to number 615,000 in 2004.2
LSD = lysergic acid diethylamide; PCP = phencyclidine.
a OxyContin® also is included with pain relievers, and methamphetamine also is included with stimulants. Estimates for OxyContin® are based only on 2004 data because age at first use was not collected for that drug in earlier years.
Source: SAMHSA, Office of Applied Studies, National Survey on Drug Use and Health, 2002, 2003, and 2004.
Based on data averaged for 2002, 2003, and 2004 (except for OxyContin®), adults aged 26 or older had lower average rates of past year initiation of nonmedical use of any prescription-type psychotherapeutic drug, each of the therapeutic drug classes, OxyContin®, and methamphetamine compared with youths aged 12 to 17 or young adults aged 18 to 25 (Table 4.1B). For example, the average percentage of previous nonusers who started using pain relievers in the 12 months prior to the interview was only 0.4 percent among adults aged 26 or older compared with 3.9 percent among those aged 12 to 17 and 3.5 percent among those aged 18 to 25. Comparisons between youths and young adults were mixed, with persons aged 18 to 25 having somewhat higher initiation rates for OxyContin® and tranquilizer misuse compared with rates among youths. In contrast, those aged 12 to 17 showed higher incidence of nonmedical use of pain relievers, stimulants, and sedatives than did young adults. However, past year initiation of nonmedical use of any psychotherapeutic drug among persons at risk did not differ significantly between youths (4.3 percent) and young adults (4.0 percent). Average initiation rates for methamphetamine also were similar for these two age groups (0.5 and 0.4 percent, respectively).
Although gender differences in average rates of initiation were small, females aged 12 or older who had not previously misused a prescription-type psychotherapeutic drug were significantly more likely than their male counterparts to initiate use within the 12 months prior to the survey (1.5 percent for females vs. 1.2 percent for males) (Table 4.2B). A similar pattern of small but statistically significant differences was found for pain relievers (1.2 percent for females vs. 1.1 percent for males), tranquilizers (0.6 vs. 0.4 percent), and stimulants (0.4 vs. 0.3 percent).
Average rates of past year initiation of nonmedical use of psychotherapeutic drugs overall were similar across geographic regions (Table 4.3B); within the separate therapeutic drug classes, the regional differences in initiation rates that achieved statistical significance were small. Among persons aged 12 or older who were at risk of initiation, the average rate of past year initial use of pain relievers was lower in the Northeast (1.0 percent) than in the Midwest (1.2 percent), South (1.1 percent), and West (1.2 percent). The initiation rate for tranquilizer misuse was higher in the South (0.6 percent) than in the Midwest (0.5 percent) and West (0.5 percent). The rate of past year initiation of methamphetamine use among previous nonusers was significantly lower in the Northeast (0.05 percent) than in any other region and higher in the West (0.20 percent) than in the Midwest (0.12 percent) or South (0.13 percent).
The average age at first use among past year initiates of nonmedical use of any prescription-type psychotherapeutic drug was 23.4 years (Table 4.4B). Again, these data are based on averages for 2002, 2003, and 2004, and they include persons aged 12 or older.
Figure 4.2 shows the average ages at first use of illicit street drugs and first nonmedical use of prescription psychotherapeutic drugs among persons who initiated use in the past year. The average age at first use ranged from 16.0 years for recent inhalant initiates to 29.5 years for recent initiates of sedative misuse. The average ages at first use for past year initiates of marijuana, PCP, and LSD3 were 17.5, 17.4, and 17.7 years, respectively. Among the specific psychotherapeutic drug classes and individual drug categories considered in this report, past year initiates of methamphetamine use had an average age at first use of 20.5 years, followed by initiates of misuse of any stimulant (21.8 years), pain relievers (22.8 years), tranquilizers and OxyContin® (24.5 years each), and sedatives (29.5 years).
LSD = lysergic acid diethylamide; PCP = phencyclidine.
a OxyContin® also is included with pain relievers, and methamphetamine also is included with stimulants. Estimates for OxyContin® are based only on 2004 data because age at first use was not collected for that drug in earlier years.
Source: SAMHSA, Office of Applied Studies, National Survey on Drug Use and Health, 2002, 2003, and 2004.
Females who initiated use of any prescription-type psychotherapeutic drugs in the past year did so at an older age, on average, than males (24.7 vs. 21.6 years) (Table 4.4B). As shown in Figure 4.3, this pattern of later average age of initiation among females held true for the misuse of pain relievers (24.1 vs. 21.2 years), tranquilizers (25.7 vs. 22.4 years), and sedatives (33.5 vs. 20.9 years).
a Estimates for OxyContin® are based only on 2004 data because age at first use was not collected for that drug in earlier years.
b Includes methamphetamine.
Source: SAMHSA, Office of Applied Studies, National Survey on Drug Use and Health, 2002, 2003, and 2004.
Among persons aged 12 or older, nearly one fifth (18.0 percent) of the estimated 14.8 million past year nonmedical users of any prescription-type psychotherapeutic drug were past year initiates (Figure 4.4 and Table 4-B). That is, they had never used until the 12-month period prior to the survey. Approximately half (50.7 percent) of past year OxyContin® users were past year initiates, probably reflecting the fact that OxyContin® is relatively new to the market.
Commensurate with the observation that most misuse of drugs starts relatively early in life, the percentage of new initiates among all past year users was higher for younger users, regardless of the class of psychotherapeutic drug. For pain relievers, for example, new initiates accounted for 47.8 percent of past year users aged 12 to 17 compared with 23.6 percent of their counterparts aged 18 to 25 and 10.8 percent of those aged 26 or older.
a Continuing users were defined as persons who initiated use prior to the past 12 months.
b Estimates for OxyContin® are based only on 2004 data because age at first use was not collected for that drug in earlier years.
c Includes methamphetamine.
Source: SAMHSA, Office of Applied Studies, National Survey on Drug Use and Health, 2002, 2003, and 2004.
| Drug | 12 or Older | Age Group (Percentages) | ||
|---|---|---|---|---|
| 12 to 17 | 18 to 25 | 26 or Older | ||
| * Low precision; no estimate reported. a Estimates for OxyContin® are based only on 2004 data because age at first use was not collected for that drug in earlier years. Source: SAMHSA, Office of Applied Studies, National Survey on Drug Use and Health, 2002, 2003, and 2004. |
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| Any Prescription-Type Psychotherapeutic Drug |
18.0 | 42.3 | 20.6 | 9.5 |
| Pain Relievers | 21.2 | 47.8 | 23.6 | 10.8 |
| OxyContin®, a | 50.7 | 72.8 | 51.6 | * |
| Tranquilizers | 23.0 | 56.0 | 26.7 | 14.2 |
| Stimulants | 25.9 | 52.8 | 26.8 | 12.6 |
| Methamphetamine | 20.4 | 60.0 | 23.5 | 8.1 |
| Sedatives | 25.2 | 48.4 | 30.7 | 18.0 |
This section reports trends in the estimated number of initiates of nonmedical use of prescription-type psychotherapeutic drugs over the period from 1965 to 2003. This information is based on NSDUH items on age at first use. When combined with information on the respondent's date of birth and the date of the survey interview, this information permits determination of the approximate date at which initial drug use occurred and provides a basis for studying longer-term trends in the annual number of initiates, incidence rates, and average ages of new initiates. As noted previously, however, these long-term trend estimates by calendar year should be viewed with caution because of potential recall bias that increases as the event of initiation becomes more temporally distant (Gfroerer et al., 2004); in particular, estimates for the earlier years are thought to be conservative. Tables showing the data contained in the graphs in this section can be found under "Web Only Reports" at http://oas.samhsa.gov/WebOnly.htm. The estimates for 1965 to 2001 presented here are based on data from the 2002, 2003, and 2004 surveys; estimates for 2002 are based on the 2003 and 2004 surveys; and estimates for 2003 are based on the 2004 survey.
As illustrated in Figure 4.5, the annual number of first-time nonmedical users of pain relievers increased from around 600,000 in 1991 to 2.7 million in 2002 and 2.6 million in 2003. In most years, the number of initiates aged 18 or older (at the time of initiation) exceeded the number under age 18, often by a considerable margin. Increases in the number of initiates of pain reliever misuse occurred in both age groups. The number of new initiates aged 18 or older appeared to reach a plateau in the year 2000, while the number of initiates under age 18 continued to increase.
The estimated number of new initiates of nonmedical use of the pain reliever OxyContin® increased from around 100,000 in 1997 to over 700,000 in 2003 (Figure 4.6). OxyContin® was approved for marketing in the United States in December 1995. Large increases in the numbers of new nonmedical users aged 18 or older started in 1999 and continued increasing in subsequent years. The number of initiates under age 18 grew slowly from 1997 to 2000 and then began to accelerate in 2001. As noted previously, all estimates of incidence of OxyContin® misuse are based only on the 2004 survey data.
Source: SAMHSA, Office of Applied Studies, National Survey on Drug Use and Health, 2002, 2003, and 2004.
Note: Incidence estimates for OxyContin® are based on 2004 data only.
Source: SAMHSA, Office of Applied Studies, National Survey on Drug Use and Health, 2002, 2003, and 2004.
The annual number of initiates of misuse of tranquilizers hovered around a half million from 1973 through 1994, then began to increase, ending at an estimated 1.3 million new users in 2000 and 2003 (Figure 4.7). The number of new users under age 18 declined from around 1974 to 1987 and began to increase again in the early 1990s.
Note: Estimates are not shown for 1965 through 1968 for initiates under the age of 18 and for those aged 18 or older due to low precision.
Source: SAMHSA, Office of Applied Studies, National Survey on Drug Use and Health, 2002, 2003, and 2004.
The estimated annual number of new nonmedical users of prescription-type stimulants hovered around 500,000 to 700,000 from 1970 to the early 1980s, then declined steadily to under 300,000 in 1991 (Figure 4.8). In a subsequent resurgence, the number of initiates increased to around 850,000 in 2000 and turned downward to end at around 760,000 in 2003. New initiates aged 18 or older outnumbered those under age 18 in most years, and trends were reasonably parallel for the two age groups.
Annual initiates of methamphetamine use increased in the early 1970s, varied between 320,000 and 465,000 from 1971 to 1987, declined to around 210,000 in 1990, increased to around 350,000 in 1995, and fluctuated around that level in the subsequent years, ending at 363,000 in 2003 (Figure 4.9).
Note: Includes methamphetamine.
Source: SAMHSA, Office of Applied Studies, National Survey on Drug Use and Health, 2002, 2003, and 2004.
Source: SAMHSA, Office of Applied Studies, National Survey on Drug Use and Health, 2002, 2003, and 2004.
The estimated annual number of new initiates of nonmedical use of sedatives was highest in 1974 at about 550,000, declined at varying rates through the early 1990s, then increased in more recent years ending at around 250,000 in 2003 (Figure 4.10).
Source: SAMHSA, Office of Applied Studies, National Survey on Drug Use and Health, 2002, 2003, and 2004.
This chapter presented findings for initiation of nonmedical use of prescription psychotherapeutic drugs (i.e., incidence), with a focus on initiation of nonmedical use in the past 12 months (i.e., past year initiation). Findings were presented for trends in past year initiation based on single-year data for 2002, 2003, and 2004. Comparisons based on other variables thought to be related to initiation were performed using combined data from the 2002 through 2004 surveys. The chapter also presented findings related to long-term trends in initiation.
1 Initiation of nonmedical use of any prescription-type psychotherapeutic drug is said to have occurred when the individual first misuses any prescription pain reliever, tranquilizer, stimulant, or sedative. For example, if someone aged 20 at the time of interview reported that he or she started using stimulants at age 20, he or she would be counted as a past year initiate of stimulant misuse. If the individual had never misused any pain reliever, tranquilizer, or sedative, he or she also would be counted as a past year initiate of misuse of any prescription-type psychotherapeutic drug. If this same individual first misused pain relievers at age 17, however, he or she still would be counted as a past year initiate of stimulant misuse but would not be counted as a past year initiate of misuse of any prescription-type psychotherapeutic drug.
2 Estimates for OxyContin® are based only on 2004 data because age at first use was not collected for that drug in earlier years.
3 LSD = lysergic acid diethylamide; PCP = phencyclidine.
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