For reasons unbeknownst to me, the first caravan arrived and then after I traded with them, they said they were leaving, hung around until midwinter, and then went insane. I know this supposedly happens when they can't find a way to leave, but there is a way out, so I'm not sure exactly what happened. I do know instead of going the (admittedly quite restricted) path leading to the edge of the map on the surface they started out going down my central staircase, so perhaps they had some notion of leaving through the caverns - even though I'm pretty sure I don't have any open ways in to them. In any case, they went crazy. One went melancholy, and his camel went stark raving mad.
My question is, what do I do now? Will they starve like normal dwarves? Right now they're both sitting quite content in my food stockpile, not doing anything. Will they just stay there forever? I'm assuming it'll cause a loyalty cascade if I try to kill them, at least with military dwarves, and they aren't really in a good place to kill them by any other means.
I remember the last time something like this happened it was because some undead attacked an elven caravan, and one of the horses fell in a dried up murky pool. He went insane, and the next time an elven caravan arrived, they all instantly went insane, too. I had to kill them all and burrow down into the murky pool to kill the crazy horse to prevent it from happening again.