from the introduction:
Mental Health Rules
One thing missing from GORE is a set of rules for mental health. This void is significant, as it is a major component of one of the classic games GORE seeks to emulate. If player characters aren't struggling to keep from succumbing to madness, or dealing with non- player characters who have obviously gone 'round the bend, the flavor of the game just isn't the same. Unfortunately, the original rules for such are not available under the Open Gaming License, which explains their absence from the GORE Core Rules.
What is presented here is not an attempt to recreate the classic mental health rules, but an all-new, original set of mechanics for covering the same ground. In addition to filling a gap in GORE's Core Rules, it can be used as an alternative system for the classic game, or for any percentile-based game using the same algorithm.
This supplement is available as a free download from basicroleplaying.com.