depression
"I was initially prescribed this medication to address both a mild sleep apnea problem and persistent depression.  Initially, it was indeed like a miracle drug.  I felt better immediately and continued so for about a year.  However, the drug then quickly became less effective and actually began to make my depression much worse.  I very briefly switched to Nuvigil, but I continued with the worsening depression and ended up having to stop the medication.  Within a few days of discontinuing the medication, I felt considerably better.  I went on to other medications to help with the depression and fatigue.  Provigil/Nuvigil has been a blessing for many people.  However, as with many medications, their continued use can sometimes backfire."