Abstract
We examined initiation patterns among different birth cohorts of people who used prescription opioids and heroin because of historical differences in drug use availability. We examined data from a community-based study of persons who inject drugs (n = 483) in California and a general population survey from the National Survey on Drug Use and Health (n = 1264) and found that individuals born after 1980 were more likely than were individuals born before 1980 to initiate opioids through nonmedical use of prescription opioids than heroin.
The increased availability of prescription pain relievers stemming from the expansion of prescription pain reliever medications in the mid-1990s may have inadvertently produced an epidemic of nonmedical use of prescription opioids. Public health researchers have identified dramatic increases in the morbidity and mortality associated with prescription pain reliever products.1 Recent public health and legislative efforts to reduce the widespread illicit use of prescription opioid pain relievers (nonmedical prescription opioid use; NMPOU) may have produced an unintended consequence of driving prescription drug users toward heroin.2 However, the start of the prescription opioid epidemic is assumed to have begun in the mid-1990s, after the introduction of extended release or long-acting prescription pain relievers (e.g., OxyContin).3
Because of these environment changes, it is expected that differences in period effects of exposure to various drugs of abuse would reflect birth cohort variations in the sequences of onset. This variation stems largely from differences in how drugs are available when each cohort reaches their peak window of initiation to substance use, which is typically tied to developmental changes in biological, psychological, and social milestones during early adolescence and young adulthood.
We have described changes in the types of opioids, either prescription pain relievers or heroin, that people use to initiate their opioid use across 4 birth cohorts (pre-1960s, 1960–1969, 1970–1079, 1980 and later). We hypothesized that initiation of opioids through prescription opioids rather than heroin would become more common for more recent birth cohorts, who are likely to have reached the peak window of vulnerability to onset of opioids during the era of the escalating availability of prescription opioid pain relievers.
METHODS
The study sample consisted of 483 people who inject drugs (PWIDs) in Los Angeles and San Francisco, California, who reported lifetime use of both heroin and nonmedical prescription opioids. We collected data between April 2011 and April 2013. We recruited PWIDs using targeted sampling methods and community outreach.4,5 For comparative purposes, we also analyzed general population survey data from 1264 persons aged 18 years and older who completed the National Survey of Drug Use and Health (NSDUH) and reported a lifetime use of heroin and nonmedical prescription opioids.6
The NSDUH is an address-based sample, but it has been criticized for underestimating the prevalence of several illicit drugs, including heroin.7 Inspection of the 2 studies permits examination of a wider range of population groups. The PWID sample may be regarded as a sentinel population of early adopters, in which signals of new and emergent drug trends may appear before they are detected in general population surveillance systems such as NSDUH.
We used data from NSDUH during the same period as the PWID sample, quarter 2 of 2011 to quarter 2 of 2013. The NSDUH consists of 4 discrete quarterly subsamples, each with a replicate design weight that can be used to generalize each quarter to the entire US population of noninstitutionalized persons. We recalibrated the general analysis weights to generalize the NSDUH sample to the sample collected in each quarter within each yearly data set. We took the birth cohort data from questions in the substance use module. Both studies asked about the nonmedical use of prescription pain reliever medications, although most of the use is accounted for by opioid medications. Furthermore, we extracted a subset of those with a lifetime use of either heroin or prescription pain relievers.
RESULTS
There were statistically significant differences by birth cohort in the prevalence of persons who initiated both heroin and NMPOU (Figure 1; Table 1). In the PWID study, there was a steady decrease in the proportion who first initiated opioid use with heroin as the birth cohorts progressed from the 1960s to the 1970s and after 1980. There was a concomitant steep increase in the proportion who first initiated with NMPOU during this progression of birth cohorts. For PWIDs born in the 1980s or later, the majority of people who used opioids had initiated by NMPOU rather than heroin. The number of PWID who engaged in onset of both substances in the same year also increased, from 8% in the pre-1960s cohort to 20% for those born in 1980 or later.
FIGURE 1—
Reversed Sequence of Heroin Initiation and Nonmedical Prescription Opioids Across Birth Cohorts in Persons Who Inject Drugs in California: 2011–2013
TABLE 1—
Reversed Sequence of Heroin Initiation and Nonmedical Prescription Opioids Across Birth Cohorts: United States, 2011–2013
| Variable | Pre-1960s, Unweighted No. (Weighted %) | 1960–1969, Unweighted No. (Weighted %) | 1970–1979, Unweighted No. (Weighted %) | 1980 and After, Unweighted No. (Weighted %) |
| California PWID samplea (2010–2013) | ||||
| Heroin | 129 (73) | 92 (46) | 33 (43) | 7 (10) |
| Prescription pain relieversb | 34 (19) | 56 (35) | 33 (43) | 46 (70) |
| Same age | 15 (8) | 14 (19) | 11 (14) | 13 (20) |
| NSDUHc (2011–2013) | ||||
| Heroin | 40 (36) | 53 (29) | 26 (20) | 69 (9) |
| Prescription pain Relieversb | 71 (52) | 127 (62) | 85 (71) | 634 (79) |
| Same age | 19 (12) | 21 (9) | 14 (9) | 105 (12) |
Note. NSDUH = National Survey on Drug Use and Health; PWID = persons who inject drugs. Prescription pain relievers include nonmedical use of prescription-type pain relievers (NSDUH) and opioid pain relievers (California PWID).
χ2 = 80.37; df = 6; P < .001.
California PWID asks about prescription opioid pain relievers, and NSDUH includes nonopioid pain reliever products (e.g., tramadol). Results did not change when restricting analyses to known opioids captured in NSDUH.
χ2 = 49 672.00; df = 6; P < .001.
In the NSDUH sample, there was a similar shift toward increasing numbers of persons using opioids before heroin, except that across all 4 birth cohorts the most common opioid that was initiated first was prescription pain relievers. Similar to the PWID sample, there was a major shift toward a greater percentage of the population initiating opioid use through NMPOU rather than heroin.
DISCUSSION
These changes in initiation patterns may be linked to several developments in the widespread availability of prescription opioids after the introduction of extended release or long-acting opioids, namely OxyContin after its approval by the US Food and Drug Administration in 1995.8 There were also public health and clinical efforts to increase access to pain reliever medicine through comprehensive assessments and the management of acute and chronic pain during this period.9 Other studies have shown how the demographics of people who use opioids have changed: heroin has become more prevalent in suburban areas and among White people.10
By showing changes in the pattern of opioid initiation by birth cohort, our findings illustrate the significant public health impact of environmental public policy initiatives on population trends involving the behavioral pattern of initiation. Because of the consistency of these findings with what is known about changes in the availability of OxyContin and prescription-type opioids after 1995, it appears that more recent birth cohorts are more likely to initiate opioid use through NMPOU than through heroin.
In the past 5 years, there have been numerous changes in policy that have restricted access to prescription pain relievers in the United States, such as the reformulation of OxyContin, which has made it hard to abuse via tampering, and the expansion of prescription drug–monitoring programs that reduce doctor shopping.11–13 Future studies will likely yield valuable information on whether these policies will reverse the trends of persons initiating opioid use via prescription pain relievers, particularly among those in more recent birth cohorts.
ACKNOWLEDGMENTS
This research was funded by the National Institute on Drug Abuse (grant R01DA027689 to R. B. and A. H. K.; grant R01DA030427 to S. P.N.).
We give special thanks to the research staff, including Sonya Arreola, Andrea Lopez, James Thing, Karina Dominguez, Jahaira Fajardo, Askia Muhammad, and Michele Thorsen.
HUMAN PARTICIPANT PROTECTION
This study received approval from the institutional review boards at RTI International and the University of Southern California.
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