Back in alpha 4 I had the "brilliant" idea to use human flesh for meals since I was always running out of meat and there was piles and piles of raider corpses out in my dumping zones. At the time I was tunnelling very deeply and very extensively into the mountain in search of metal. I was mining from map edge to map edge so my pawns were spending a lot of time walking through narrow, dark, hideous tunnels to the current mining zone.
For the first day everything seemed fine, then I started getting warnings of imminent mental breaks. Lots of them. The tunnels were so long that people were getting tired and hungry just commuting to and from the mining site. The -15 to mood from cannibalism was just enough to cause everyone who went down those tunnels to start to lose it. Something like 15-20 colonists risked imminent mental breaks over the course of 10 minutes or so, and I was frantically conscripting and unconscripting people so they would abandon their current job and get some food and rest.
Then two of my best and most skilled colonists (Ritter and Keuneke) lost it and went on a psychotic rampage deep in the tunnels. They were armed with the best weapons in the colony. I ordered people away from the area, forbade everything in the tunnels and put guards in the populated area of the colony, expecting a blood bath. As it happened, as chance would have it, on the very edge of the populated area, they both turned into the same tunnel and faced each other over a short distance, with the best, and most deadly, weapons in the colony ...

... which they used as clubs ...
Ritter was knocked unconscious in the melee by the larger Keuneke, who was in turn beaten into submission by the guards. I ordered them both arrested and shut down my cannibal production line before anyone else went nuts. Relieved that I hadn't lost anyone, I did a quick check of the colonists and found that one more, Zeppy, had gone nuts and was wondering the wastes. When the guards found her, she was totally oblivious to the squirl that was attacking her.
Ritter and Keuneke I managed to re-recruit after only a few days. Zeppy however took many, many weeks to recover from the horror of being fed human flesh. My wardens were reporting that Zeppy just paced around her cell all day, muttering "They made us eat people ... they made us eat people ..." over and over again.
I dumped all the unused human flesh outside the colony in the end.