narcolepsy
"I started taking Provigil about a year ago when it was suspected I had narcolepsy.  I was tested and found it was Idiotic Hypersomnia (lack of melatonin) they call it Idiotic because they don't know what causes it. Provigil works one day for me then not the next.  You can only take 200mg max per day. I went off it and on Ritalin.  I am awake without any ill effects.  I have recently been tested again for narcolepsy and was found that I am narcoleptic.  The test given last year was done incorrectly (without my C-pap), it was supposed to be done WITH it on during my sleep study. All is good now."