Illicit Methylphenidate Use in an Undergraduate Student Sample: Prevalence and Risk Factors

Christian J. Teter, Pharm.D., Sean Esteban McCabe, Ph.D., Carol J. Boyd, Ph.D., Sally K. Guthrie, Pharm.D.

Disclosures

Pharmacotherapy. 2003;23(5) 

In This Article

Discussion

Approximately 3% (57 students) of our sample of 2250 undergraduate college students had used methylphenidate in the past year without a doctor's prescription. This is consistent with the limited prevalence data published in the literature regarding illicit use of methylphenidate among adolescents. For instance, the Monitoring the Future study, which tracked illicit methylphenidate use in nationally representative samples of 12th grade students, found that illicit use has increased dramatically over the past 5 years, with a current annual prevalence of approximately 3%.[12] Similarly, an Indiana survey revealed that approximately 4% of 12th grade students in that state had used nonprescribed methylphenidate in the past year.[17] The Monitoring the Future and Indiana sample populations both consisted of 12th grade students, not college populations; in fact, limited data have been published on illicit methylphenidate use among college students. One single-institution study found that more than 16% of the students surveyed (283 students) at a 4-year public liberal arts college had tried methylphenidate for nonmedical purposes.[18] Because there are significant differences in drug-using behaviors among different colleges and universities,[4] the extent of illicit methylphenidate use among college students nationwide remains unknown, although it appears to be a growing problem on some campuses.

Further evidence illustrating this potentially serious public health issue comes from a variety of anecdotal case reports of methylphenidate abuse in the literature,[19,20,21,22,23,24] as well as empirical evidence that methylphenidate has abuse potential.[25] According to an extensive literature review, in 48 of 60 studies (80%) assessing the reinforcing, discriminative-stimulus, or subjective effects of methylphenidate in nonhuman and human subjects, methylphenidate appeared to have an abuse potential similar to that of D-amphetamine and cocaine.[25] Furthermore, methylphenidate and cocaine show similar pharmacokinetic and pharmacodynamic profiles in the human brain[26] and have very similar actions at the dopamine transporter.[27] Thus, it is possible that methylphenidate has an abuse potential similar to cocaine or D-amphetamine. However, according to the National Institute on Drug Abuse Community Epidemiology Work Group, actual abuse rates for methylphenidate appear to be much less than those for cocaine and D-amphetamine in the United States.[28]

In our sample, rates of cigarette smoking, alcohol use, and illicit drug use were significantly higher among undergraduate college students who used illicit methylphenidate than among those who used prescribed stimulants or who did not report any stimulant use. Not only were illicit methylphenidate users more likely to be polydrug users, they were also more likely to have begun drug use in high school or earlier, as compared with the other two groups. For instance, 91% of past-year illicit methylphenidate users had used marijuana in high school or before.

Notably, the drug-use behaviors of students using prescribed stimulants more closely resembled the drug-use behaviors of the nonstimulant users than they did the illicit methylphenidate users. This finding accords with the conclusions of a research group who determined that effective treatment of ADHD with psychostimulants, such as methylphenidate, may decrease young patients' risk of developing a substance use disorder.[29] These researchers, after controlling for subjects' age, socioeconomic status, lifetime risk of conduct disorder at baseline, and lifetime history of substance abuse disorders in the subjects' parents, found that pharmacotherapy was associated with an 85% reduction in the risk for substance abuse disorders in youths with ADHD.[29] Although there is disagreement about the exact relationship between ADHD, psychostimulant use, and the risk for developing a substance use disorder, our sample of students using prescribed stimulants exhibited rates of substance use that were similar to those of nonstimulant users. These students may have experienced a protective effect from substance use by effective treatment with methylphenidate, although larger samples and additional information regarding ADHD diagnosis would be needed to establish this association clearly.

It is well known that alcohol or drug use behaviors cluster together with other problem behaviors.[30] Our findings suggest that the factors associated with illicit methylphenidate use are very similar to those previously found to be associated with use of other illicit drugs among college students.[1,31] Having a greater number of sex partners and engaging in frequent partying in college have been shown to be significantly associated with higher rates of marijuana[31] and Ecstasy[3] use. However, although these behaviors are associated with illicit drug use, the causal role of illicit methylphenidate use in our students who reported other risky behaviors or negative alcohol- or drug-related consequences cannot be clearly established.

According to the Drug Enforcement Administration, the overall production (aggregate production quota) of methylphenidate has increased dramatically since 1990.[32] This increase in availability may partly reflect an increase in diversion, but it also may be indicative of a dramatic increase in recognition and diagnosis of ADHD, combined with realization that ADHD symptoms often continue into adulthood.[33] Although we did not set out to examine the diversion of prescribed methylphenidate, we found an apparent relationship between illicit methylphenidate use and prescription stimulant use in university residence halls. For instance, in six residence halls where there was no reported prescription stimulant use, there was also no reported illicit methylphenidate use. However, in three of four residence halls where prescription stimulant use was present, illicit methylphenidate use was reported. Limited sample sizes prevented us from detecting statistically significant differences in illicit methylphenidate use among particular residence halls. More research is needed in this area because diversion of prescribed stimulants has been documented among children and adolescents in both Canada and the United States.[34,35]

Several limitations need to be considered when weighing the potential implications of this study. The survey question regarding prescribed stimulants included "weight loss pills" as an example in addition to "Ritalin," which limited our findings. Since we cannot assume that 100% of respondents answering yes to the prescription stimulant response had taken methylphenidate for ADHD, based on information provided by the Drug Enforcement Administration and the Council on Scientific Affairs of the American Medical Association, approximately 80% of prescribed methylphenidate is used for children diagnosed with ADHD,[32] and more than 90% of stimulant use for the treatment of ADHD in the United States is methylphenidate.[11]

The survey question assessing illicit methylphenidate use did not carry the same limitation because it listed only Ritalin as a response. We did not determine the quantity of illicit methylphenidate that students used on each occasion, the reasons for use, or whether any respondents had taken methylphenidate intranasally.

The power of our statistical analyses, in particular the multivariate logistic regression, was limited by the number of students who reported prescribed stimulant use (25 students) and illicit methylphenidate use (57 students). Our findings regarding possible diversion were limited because our analysis was based on a probability sample of undergraduate students living in residence halls. Therefore, we could not accurately assess actual diversion rates based on the entire residence hall population. Also, we did not ask how illicit methylphenidate users were obtaining their methylphenidate. Finally, our study population consisted of a predominantly white and affluent group of undergraduate college students. More research is needed to compare our findings with those resulting from more diverse samples, including young adults not attending college.

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