depression
"I have been on numerous antidepressants that seem to wear out over time.  I last had this experience with paroxetine.  My doctor suggested Ritalin as an aid to make the paroxetine work better.  What a world of difference!  There's not much information out there about this, and I am sure there must be downsides.   This works for me like nothing else.  I am very careful with it, but I feel there are more upsides than otherwise."