The Malkavian in our group is played by a trigger-happy player who tends to use the cheap lower ranks of Dementation multiple times per session, mostly on his own party. Dementation is the vampiric discipline that infuses others with "madness", the first ranks are Passion (extremely strengthen or weaken an emotion in someone) and The Haunting (give someone more or less subtle hallucinations). The latter costs one blood point, the former is free.
We've established early on that we are ok with this, but by now this behaviour has started to alter some PCs noticeably (or, realistically, should do so), as they become haunted or their emotions are heightened/dampened for weeks after a good roll and we can't skip time IT, due to plot. The characters are all neonates and don't suspect their buddy to be responsible for all the weird emotions lately, they mostly don't even realise there is anything off about the constant paranoia and mood swings, it might be a side effect of being thrown into this undead society.
The way we've been playing so far was that The Haunting would haunt one character once and then play out, disregarding later attempts to invoke the same again. However, every use of Passion would alter one emotion of the "affected" player's choice (we went with the most present at that moment) for the time decided by the dice. This allows Passion to stack. One PC sort of became the favourite target for these jokes and is now juggling an emotional turmoil that was not part of the character's concept at all.
So, to the question: Is there anything in the rules that supports or contradicts the stacking of Passion? And also, how should it be handled if it comes up so often? Is there more about this in the Clanbooks, maybe? The way it is now, I feel like the whole discipline is just a shortcut to cause chaos and disruption to the game, without any apparent gain for anyone. What I really want to know then, I guess, is more along the lines of How to balance the use of Dementation in a game where it is used heavily PvP?