Just a question: if the Ritalin worked, why did you stop taking it? I know there could be a multitude of reasons, but could you go back to Ritalin? I don't have any personal experience with stimulants working for my depression (though I have taken Vyvanse before for trying to treat my negative symptoms of schizoaffective disorder). I don't think they really did anything for me.

Also, what about antidepressants? You didn't mention that in your post, so I wonder if you've tried any? I'm assuming you have since you said you had treatment-resistant depression.