Hey mgracer13-great question! My answer is from my experience that each SSRI works a little differently but eventually they all "poop out." I have to alter my med cocktail quite often to feel okay, but I'm bipolar which is different than having MDD. You might ask your pdoc about adding Aplenzin, or Welbutrin SR in combination with Zoloft then trying Vibriid or an SNRI, like Cymbalta, before adding an AAP like Abilify or Latuda. I'd make sure they're weight neutral before you start them. All the best!!