I've spoken to my psychiatrist but he doesn't think the Zoloft is pooping out because I was on it for more than 15 years without any problems at all. It was only when I tapered down from 150mg to 50mg a day that my depression and anxiety recurred, and then when I reinstated the Zoloft, my depression and anxiety did improve, just not as much or as quickly as before. My guess is that during the 2 years that I tapered off the Zoloft, my depression was gathering a head of steam on a biological level. I asked about switching meds, but my psychiatrist said there is a risk that a different drug won't work as well, and since I did respond to the reinstated Zoloft, it made more sense to augment. As for what's happening right now, I suppose the Zoloft could be pooping out, but it seems more likely that reducing from 1mg to 0.5mg of Abilify is the culprit. It does surprise me that such a small dose could make a difference, but apparently it's a powerful medication, and I did reduce my dose by 50%.