It depends. There are different definitions of treatment-resistant depression. Some people say it is after four medications have not been effective. In this case (and in cases where many other meds have been prescribed), there are a vast array of meds and combinations of meds that you can try. Other than that, someone mentioned ECT and then there is something else. I forget the name but it has something to do with someone holding a device that is kind of like a magnet to stimulate parts of your brain that are causing the depression. Sorry I don't have more info right now but it is something you might want to look into. I know that both ECT and the magnet therapy have very high success rates and very few side effects. There are always options!