This study describes the prevalence of various forms of nonmedical use of prescription stimulants. In our sample of college students, 18.0% of ADHD- students used prescription stimulants nonmedically at least once in their lives, meaning they had used someone else’s medications. The comparable proportion among students who were medically using prescription stimulants for ADHD (ADHD+) was about the same: 15.6% (7/45). However, when overuse of one’s own ADHD medications is included in the definition, 33.3% of ADHD+ students could be defined as nonmedical users. Thus, even small changes in the definition of nonmedical use can greatly affect the estimated prevalence.
Earlier studies of clinical samples did not reveal major problems of abuse or diversion of prescription stimulants,25–27
while more recent studies have highlighted the possibility of overuse among children treated for ADHD. Wilens et al.28
reported that of 98 patients with ADHD, 11% diverted their medication, 22% overused it, and 10% used their medication to “get high.” Interestingly, in that study, 83% of the “misusers” in that study had a diagnosis of either a conduct disorder, substance use disorder, or both. In a separate study, Williams et al.29
reviewed the medical charts of 450 adolescents and found that 44% of ADHD patients used their own medications nonmedically.
For the purposes of comparison with prior literature, we prefer to report prevalence estimates based on nonmedical use of someone else’s prescription stimulants: 13.0% wt
for lifetime and 10.4%wt
for past year. These results are somewhat higher than the corresponding estimates (8.3% and 5.9%) reported in one large college student study which, like the present study, included many types of prescription stimulants.20
Moreover, by capturing multiple forms of prescription stimulants, we obtained prevalence estimates that are higher than the 2005 NSDUH, which reported that 5.8% of 18 to 25 year olds used methylphenidate at least once in their lifetime.30
Other cross-sectional studies of college students reveal a wide range of prevalence estimates for lifetime NPS, from 6.9% to 35.5%.10, 11, 14, 31, 32
The studies vary with respect to age range of the samples, response rates, and the types of stimulants assessed; however, several interesting and consistent findings have emerged and have been replicated in the present study. Consistent with earlier studies,13, 32
we found that NPS appears to be generally infrequent and sporadic, with the majority of NPS+ individuals using them less than 12 times in their lives (85.3%). We also found that most students nonmedically use stimulants “purposefully” as an academic aid, that is, to help them study or cram for exams and write papers.11, 31
We also found that the overwhelming majority of college students obtain prescription stimulants from friends, who either have or do not have a legitimate prescription.13, 33
Lastly, consistent with McCabe et al.,32
we find it noteworthy that the students taking prescribed ADHD medication were outnumbered by lifetime nonmedical users of prescription stimulants, at a ratio of nearly five to one (45 vs. 218).
In this study, the proportion of lifetime nonmedical users who cited recreational reasons for use (i.e., getting high or staying awake to party) was somewhat lower than in previous reports, which yielded estimates ranging from 19.3% to 70%.11, 13, 20, 33
Similarly, inhalation of stimulants (14.2% of lifetime nonmedical users) was also less prevalent in this study than elsewhere. Although these differences may be partially attributable to methodological differences in the wording of questions, mode of administration, or geographic differences; it seems noteworthy that the college student samples in these prior studies have all been considerably older, whereas the present sample was restricted to first-year students aged 17 to 20. Future studies with this cohort will determine the extent to which recreational NPS and inhalation might become more prevalent later in college.
In our study, multivariate analyses revealed that both overuse of medically prescribed stimulants for ADHD and NPS (using the strict definition of using someone else’s medication) were independent risk factors for past-year use of other illicit drugs, even controlling for demographics. These findings confirm those from other studies that reported a strong association between NPS and polydrug use.10, 33, 34
A meta-analysis by Wilens et al.35
concluded that the balance of evidence from six outcome studies supported the notion that individuals who were treated for ADHD were at a lower risk for developing a subsequent substance abuse disorder than children with untreated ADHD. While our study cannot speak to the association between untreated or undiagnosed ADHD and risk of illicit drug use, our finding that overuse of prescription stimulant medication was independently associated with past-year illicit drug use warrants further study. One clear implication is that college students being treated for ADHD might need more careful monitoring for the persistence of ADHD symptoms, inconsistent compliance with treatment (e.g., overuse), and possible illicit drug use. Further studies with this cohort are underway to uncover their diagnostic and treatment history with respect to ADHD, including the age at which they were first diagnosed with ADHD and whether they followed their treatment regimen consistently; the possibility of conducting clinical assessments of ADHD in the sample is also under consideration.
The findings of this study must be tempered by the following limitations. First, while the sample was ascertained using stratified random sampling methods and not simply a volunteer or convenience sample, students were sampled from a single university, and thus, the results might not be generalizable to smaller private colleges or universities in other regions of the U.S., or to populations other than college students. Second, we defined our ADHD+ sample as the individuals who were medically using a prescription stimulant for ADHD; therefore, there is a possibility that some students in our ADHD- group would have been diagnosed with ADHD if they had received a clinical assessment. Also, although interviewers were trained to convey a non-judgmental attitude and repeatedly reassure participants about confidentiality throughout the interview, we cannot rule out the possibility that some participants underreported their drug use behaviors due to social desirability effects. Lastly, the analyses performed are cross-sectional and do not shed light on the longitudinal patterns of overuse or NPS. For example, we cannot ascertain from our statistical models whether the associated illicit drug use occurred before, after, or during the same time period as the NPS. As part of the longitudinal design of the study, the initial interview focused on lifetime drug use, whereas subsequent assessments capture more recent intervals of use; therefore, data presented here are limited with respect to details of recent drug use. Moreover, interviews were conducted throughout an eight-month period spanning the academic year, and therefore we cannot determine how many students may have initiated NPS and/or treatment for ADHD at some later point during their freshman year. Kaloyanides et al.36
showed that students who began medical use of prescription stimulants in college, in contrast to initiating medical use earlier in childhood, were more likely to have drug problems than individuals who had not used prescription stimulants medically.
Implications for Clinicians
These findings, together with the growing body of literature on the subject of NPS among college students, suggest a need for additional clinical guidelines for physicians who prescribe stimulant medications to older adolescents who are college-bound. The American Academy of Pediatrics published clinical practice guidelines for the assessment and treatment of ADHD in school-aged children in 2000.1
While extensive information was provided with regard to involvement of parents in the process of assessment and treatment, no mention was made of the risks associated with NPS.
We found that 26.7% of students who medically used a prescription stimulant for ADHD overused their medication, and that three-quarters of NPS+ individuals had obtained prescription stimulants from a friend who had a prescription. These findings suggest that, for ADHD patients in high school and college, physicians should be aware of the possibility of overuse and/or diversion of stimulant medications. Guidelines for clinical practice should include recommendations for age-appropriate educational messages tailored to these older adolescents. For example, patients should be cautioned against diverting their stimulant medications or using their friends’ medications. Although this study did not measure co-ingestion of prescription stimulants with alcohol and other drugs, we found that nonmedical use occurred in the context of “partying” for a number of students, consistent with prior studies documenting significant co-ingestion.11, 33
Physicians should therefore caution patients about the health risks associated with co-ingestion, especially considering recent evidence of the potential for serious adverse effects resulting from interactions of stimulant medications with alcohol and other drugs.33, 37
If, as suggested by the current study, the college environment poses especially high risks for ADHD patients with respect to nonmedical prescription drug use and other drug involvement, then the transition to college is an especially important time for physicians to emphasize these messages. Accordingly, physicians should monitor their ADHD patients for overuse of their medications and other forms of illicit drug use via both drug testing and self-report assessment tools.
Implications for Parent Education
If the findings of the study are replicated and confirmed, this line of inquiry has potentially important implications for prevention of NPS. First, prevention activities can be targeted toward parents. Parents of students with ADHD should be given general information about the possibility of overuse and misuse, especially if their child is in college and having to face the challenges inherent to college life, such as a heavy class schedule and multiple assignments due at similar times. Moreover, we believe that the absence of parental supervision and increased independence associated with being in a college environment may also create more risk for NPS among students with ADHD as compared to being in secondary school, where parents may be able to more closely supervise therapeutic dosing for their adolescent.
Parents of students without ADHD can also be targets for prevention messages aimed at helping them learn to recognize when their college-age child is using someone else’s prescription stimulants, and to respond proactively. Comments provided by a few respondents in our study have highlighted the possibility that in at least some cases, parents are not concerned about this behavior and sometimes even encourage it if it will lead to better grades. For example, one respondent explained that parents “understand because it relieves the pressure.” Teter et al.12
reported that nonmedical users of prescription stimulants actually have lower grades than students who do not take prescription stimulants nonmedically. Similarly, in our own sample, NPS was linked to lower grades by the end of the freshman year of college, and this association was mediated by the effect of skipping class more frequently.38
Given this information, parents should not encourage or simply turn a blind eye to this behavior; rather, they should strongly question the argument that their child’s NPS helps them meet the challenging demands of a college workload. Parents should caution against this practice because of legal risks and unknown health risks associated with taking another person’s prescription stimulants. Moreover, nonmedical use of any prescription drug should serve as a “red flag” to parents since we and others39
have consistently demonstrated the link between nonmedical use and illicit drug use and heavy drinking. Moreover, in this study we report a significant association between NPS and dependence upon alcohol and marijuana. It is possible that students who are drug dependent are more likely than non-dependent students to turn to NPS as a way of compensating for decreases in academic performance. We plan to test this hypothesis prospectively in our longitudinal study by examining incident NPS among dependent and non-dependent marijuana users.
The findings of this study have implications for college administrators and campus health professionals. The effectiveness of prevention programs that specify both legal and health risks of nonmedical use of prescription drugs needs to be evaluated and could be integrated into efforts to curb tobacco and alcohol use. Placing NPS in the same context as illicit drug use—which is valid given the strong association between the two behaviors—may serve as a way to discourage students who are “on the edge,” that is, those who have had the opportunity but have not yet used the drug. The fact that less than 20% of students are using prescription stimulants nonmedically in their first year of college may be useful in crafting social marketing strategies aimed at increasing students’ awareness that this behavior is not normative.
From a methodological standpoint, researchers should arrive at a consensus regarding terminology, rather than continuing to use a variety of terms, such as “misuse,”13, 33
“illicit use,”12, 31
and “unsanctioned use.”41
In our estimation, NPS is a difficult behavior to assess due to the high variability in how participants subjectively interpret the wording of questionnaire items, and these difficulties are compounded with populations being treated for ADHD. Although interview methods may be subject to other limitations, such as underreporting of socially undesirable behaviors, we believe they have distinct advantages over self-administered formats for investigating a behavior as complex as NPS. Moreover, we find no evidence of underreporting based on comparisons of our prevalence estimates with prior studies, especially considering that our sample of college freshman was younger than students in most prior studies. In this study, we attempted to distinguish overuse of one’s own prescription stimulants from use of medications that were not legitimately obtained, yet we observed little substantive differences between these behaviors. We therefore recommend that researchers use a broad definition of nonmedical use with sufficient follow-up questions to clarify the context in which the drugs were obtained and used.
Another promising area of research pertains to understanding the impact of abuse-resistant formulations of prescription stimulants, and the use of non-stimulant alternatives such as atomoxetine on NPS. In this study, the most common nonmedically used prescription stimulant was amphetamine-dextroamphetamine (89.3%), followed by methylphenidate (25.8%) and lastly, methylphenidate extended release (13.8%). This finding is somewhat expected because methylphenidate extended release is formulated to be abuse resistant.18
Our finding that amphetamine-dextroamphetamine is nonmedically used more widely than other stimulant medications is consistent with prior research.20
Other studies are needed to confirm that the immediate-release form of amphetamine-dextroamphetamine is nonmedically used more frequently than the extended-release forms. Prescribing abuse-resistant formulations might be a prudent strategy for physicians to limit nonmedical use, while still gaining therapeutic benefit for ADHD patients.19
Our sample will be followed longitudinally to better understand the development of possible consequences of NPS. In another study of this cohort, we documented that between the freshman and sophomore years of college, 11.7% of NPS-naïve students became new nonmedical users of prescription stimulants, and 60.7% of prior nonmedical users continued to use from one year to the next.21
Further study is warranted to examine whether overusers of prescription stimulants for ADHD have similar or different incidence rates or rates of continuation. Future work with this cohort will examine NPS-related risk of other illicit drug problems, including health problems in the transition to adulthood, and will aim to understand whether or not students who use prescription stimulants nonmedically for academic performance purposes subsequently continue using stimulants in order to improve occupational performance. This line of research will clarify the extent of harm to public health that is associated with nonmedical use of prescription stimulants.