narcolepsy
"I am 2 months shy of having used Provigil for 10 years.  I have no physical side effects from it, which is pretty good since I am in my late 60s.  It was more effective at keeping me awake when I first started using it, but it also made me a little nervous.  These days it is usually effective, but sometimes not, but the good news is that I am much calmer than I have been in years.  If this medicine seems to lose it's effectiveness, don't give up.  Stop taking it for a little while (a week or two) and it will work again just fine.  All and all this medicine has given me back my life, except for driving me to the poor house."