They keep the brain from being overwhelmed. But in the case of nerve damage
or a nerve system malformation (Like Chiari
or Fibromyelgia) they can help tremendously with chronic pain.
I only know of Paroxetine and Cymbalta from what I've read, but to be honest, I think the risks of side-effects are pretty dangerous, I'd suggest you ask your doctor about Lyrica instead. Lyrica also can have side effects, but so can any drug.