narcolepsy
"I am a student.  Was having sudden sleep blackouts when reading, or sitting in lecture. Also "brownouts" where, for example, listening to someone talk, I suddenly shut down and "sleep" but they think I am wide awake. Brownouts not good for driving! So, first day I took it, I read 3 chapters for a test that was two hours away. I stayed alert, and RETAINED every bit. No more blackouts or brownouts. Headache for the first week or so. Also, for the first few days, I hardly slept. Even stayed up all night a few times. I have learned to tweak it a bit, break the tablets, take a small amount at first and more later if I need it, but not overdo it. No changes in personality, other than being more competent at life."