. >> alan desantis: what are we observing?uric: alan desantis, a communications professor at the university of kentucky, says he was so baffled by his students' casual use of adderall, he decided to study it. >> desantis: when we asked the students why they use a.d.h.d. stimulants, many refer to it as "a steroid for the brain." >> couric: in a survey of nearly 2,000 students at the university, desantis found that 34% of undergraduates overall had taken attention deficit drugs illegally, without a prescription. and that number climbs the longer they're in school. >> desantis: if you were to ask what percentage of juniors and seniors are using a.d.h.d. stimulants, the number is well above 50%, pushing 60%. and if you add in juniors and seniors who are in fraternities and sororities, the number is up about 80%. >> couric: and he discovered where all the pills are coming from. >> desantis: about 4% of our college campus has, actually, legal prescriptions. but what we have found is that, while they may get 30 doses, they very rarel