I have resistant bp depression. Of the 24 I have been on over the decades, four have worked:

Least Effective--Cymbalta. Way better than SSRIs.
Better--Wellbutrin. Lot better.
Better yet, Lithium--saved my life in 2008. Amazing.
Best--an NMDA antagonist similar to Namenda but not Namenda. Total, utter miracle from God. By far the best. Cannot take due to SE, tragically.

My depression is glutamate- and dopamine-mefiated. Serotonin plays zero role in my brain