Just did some !!science!! with the [CRAZED] tag, by giving one caste of dwarves an interaction that caused them to go temporarily berserk periodically. I'll report my findings:
1. Creatures with the [CRAZED] tag, whether by default or as a syndrome result, will attack anyone and everyone they see: friends, enemies, giant animals, and other berserk society members alike.
2. During the time that they are berserk, they are not considered members of the society at all, they will not be listed among your citizens, and killing them while berserk will not cause a loyalty cascade. If the only remaining citizens have gone berserk, this will result in an immediate 'game over' (this is the reason why I gave the ability to only one caste).
3. If the syndrome has a limited timespan, once it times out, they will return entirely to being normal members of society. Even if they are in the middle of a fight with a sane citizen, once the madness wears off, both creatures stop fighting immediately and return to daily work.
4. The deaths of creatures killed by a berserk individual outside of the view of sane society members will not be reported, and they will be considered 'missing', even if the one who killed them returns to normal.
5. I am not sure how the justice system treats murders committed by a berserk citizen. When checking the thoughts of both formerly berserk citizens and non-berserk citizens who witnessed an assault or were assaulted themselves, they both seem to consider the attacks as being committed by an unrelated third party (the thoughts of formerly berserk citizens will not include anything they experienced when berserk, though they will have their victims listed under 'kills'). In Legends mode, berserk creatures who have committed assault will be recorded as enemies or former members of societies, though this does not seem to have an effect during the gameplay itself.
6. Relationship status is not clearly affected by assaults by berserk creatures - friends will remain friends, and as previously mentioned, once the berserk syndrome ends everyone will simply behave as if nothing had happened. However, after a period of time, I did spot one non-berserking dwarf attacking a particular periodically-berserking dwarf on sight, even when the periodically-berserking dwarf was in a sane state (she would run away when this happened). I'm not sure what caused this particular event to happen though (for reference, these two dwarves were the last ones left).
Edit: On second thought, this research may have been faulty, since it all occured outside without any work actually being assigned, it is possible that they could have simply been running away from each other as opposed to 'returning to work'. Will retest.
6. I'm not clear on the precise details as far as the loyalty of formerly-berserk citizens is concerned, however, there are times when citizens will treat a formerly berserk citizen as an enemy for all intents and purposes, running away or attacking as per their personality/combat skills. The key factor, I think, is whether or not they witness the berserker actually murder someone. I placed several non-berserkers and one periodic-berserker together in a small burrow and they would behave as normal, hanging out together when she was sane and then running off when she went mad, then returning to the burrow after the madness passed, but once she caught and killed one of them, they began treating her as an enemy even when not berserk. It should be noted that this particular berserker had killed before being assigned to the burrow, and a particular cat had already been attacking her on occasion. I guess the cat witnessed the murder but nobody believed him...