Via Matt. Molly Young has the best essay I've ever read on prescription drug addition online at n+1. She came from a well-balanced family in San Francisco to an East Coast Ivy League university where she discovered Adderall, a drug typically prescribed to kids (and adults) with ADHD. In the essay she does a good job of carrying the reader through the addiction, talking about the various ways she justified it to herself:

Of course, I could have studied in college without Adderall, just like I did in high school—I just couldn't have studied with such ecstasy. Theoretical texts, in particular, were transformed into exercises as conquerable as a Tuesday crossword. I could work out in the gym with a Xeroxed packet of Gayatri Spivak perched on the elliptical machine in front of me, reading and burning calories at the same time. The efficacy of the multitasking was exhilarating. On Adderall, the densest writing became penetrable. I had an illusion of mastery, at least, that lasted long enough to write the necessary papers and presentations. I could never remember what I had written the next day, but I justified this forgetfulness as an accelerated version of what would happen anyway after I graduated.

She also talks about how easy it is to obtain the drug, saying faking ADHD is a "cakewalk," talking about how easy it is to buy extras from friends, and ordering the drugs over the internet with all those encrypted catalogs.  It's a private struggle, she says, "the drug is less talked about than exhibited."

I've never taken prescription drugs to help myself concentrate, but I've know people with family members who struggled with such addictions. To me sometimes this is about confidence and the high-pressure situations we put ourselves in. In highly competitive environments, like an Ivy League school, everyone is brilliant, so you must be more focused and dedicated than everyone else. For some, it is success that is the drug and Adderall is merely the means to that end.