GURPSよろず

Derangement
　Derangement represents lasting mental harm resulting from Sanity-Blasting Fright Checks, excessive Stress, or (depending on the campaign) bad drugs, sentient brain parasites, malevolent magic, and evil experiments. At the end of any day that brings no new Stress or Derangement, someone with Derangement may roll against Will, with success meaning he sheds -1 in Derangement penalties.

　The care of a proper therapist with Psychology (Clinical) or Physician (Psychiatric) at 12+ gives +1 to this roll – and the therapist can roll against his skill once a day to erase another -1 in Derangement.
The GM may apply Derangement as a penalty to Influence rolls as well as to Fright Checks. It’s easy enough to pass as sane when just sitting around (explaining why there’s no reaction penalty), but a loose grip on reality is harder to hide when actively trying to manipulate others. Derangement also penalizes any roll required to establish sanity; e.g., before a judge or when interviewing to leave the madhouse.
Fearlessness never offsets Derangement!

Derangement Limit: A character’s Derangement limit is also -Will.
After that, convert further Derangement into permanent mental disadvantage points!