Almost any med can cause an anti reaction when coming off it. It is because the body adapts to the med. If you are on a blood pressure med and you just stop it, your blood pressure will be higher than before treatment.

If someone is already prone to psychosis, it might just take a little nudge for things to get worse.

These things usually level out after a bit though. Coming off meds gradually and carefully gives the body a chance to balance up the loss of the med, while stopping faster might cause more of a reaction. It is basically common sense.