" Between 1982 and 1992, among 12th graders levels of amphetamine use in the past 12 months (other than use that was ordered by a physician) fell by nearly two thirds, from 20.3% to 7.1%. Levels among college students fell even more over the same interval, from 21.1% to 3.6%. During the relapse phase in the drug epidemic in the 1990s, annual amphetamine use increased by about half among 8th and 10th graders between 1991 and 1996, and also increased among 12th graders and college students between 1992 and 1996. After 1996 the age groups diverged, with amphetamine use declining gradually and substantially among 8th graders—where use is now a fraction of what it was in 1996 — but continuing to rise among 12th graders (and eventually 10th graders), college students, and young adults until about 2002. The declines continued in the upper grades through about 2008 but through 2013 for 8th graders. Since 2009, annual prevalence has increased among 12th graders (from 6.6% to 8.1% in 2014), perhaps as a result of more students using amphetamines to help their academic work. Among students in college, amphetamine use rose even more sharply from 5.7% in 2008 to 10.1% in 2014, likely for the same reason. Young adults, who include the college students, showed less of an increase over the same interval, from 5.3% in 2008 to 8.0% in 2014. The pattern of cross-age-group change suggests a cohort effect at work for amphetamine use. Since the late 1990s there has been a greater difference between use among 8th graders and use by older students, suggesting that an age effect has emerged, possibly due to the older students becoming more likely to use amphetamines to aid their academic performance. (“To help me study” was the highest endorsed reason 12th graders gave for amphetamine use in 2012 and the third highest in 2014.)
"Among 12th graders, the increase in nonmedical use of amphetamines (and a concurrent decrease in disapproval) began in 1993; this followed a sharp drop in perceived risk a year earlier (which, as we have noted for a number of drugs, often serves as a leading indicator). Following a period of decline, perceived risk among 12th graders increased gradually from 1995 through 2009.1
" Use of the stimulant drug Ritalin outside of medical supervision showed a distinct increase around 1997 — with annual prevalence among 12th graders going from 0.1% in 1992 to 2.8% in 1997 — and then stayed level for a few years (see Appendix E, Table E-22). Because of its increasing importance, a differently structured question was introduced for Ritalin use in 2001 (2002 in the follow-ups of college students and young adults). This new question, which we prefer to the original, does not use a prior branching question and produced somewhat higher prevalence levels. Results from the new question suggest an ongoing decline in Ritalin use, with prevalence levels in 2014 less than half of what they were when first measured in 2001-02.
" Another stimulant used in the treatment of the symptoms of attention deficit hyperactivity disorder (ADHD) is the amphetamine drug Adderall. A new question on its non-medical use was introduced in 2009; annual prevalence levels in 2009 through 2014 were higher than those for Ritalin in all five populations. This suggests that Adderall may have to some degree replaced the use of Ritalin and may help to account for the declines that we have been observing for the latter drug. Annual prevalence of Adderall changed rather little between 2009 and 2014 in 8th and 10th grades, although the levels seem to be drifting down. In 12th grade, however, annual prevalence has risen from 5.4% in 2009 to 7.6% in 2012, followed by non-significant declines over the next two years. The absolute prevalence levels in 2014 are fairly high, particularly among 12th graders (6.8%), young adults (7.8%), and college students (9.6%)."
Miech, R. A., Johnston, L. D., O’Malley, P. M., Bachman, J. G., & Schulenberg, J. E. (June 2015). Monitoring the Future national survey results on drug use, 1975–2014: Volume I, Secondary school students. Ann Arbor: Institute for Social Research, The University of Michigan.