Keith Herber discusses how in his "Haunted House" scenario for Call of Cthulhu, characters are driven insane by their attempt to unravel the game's mysteries. Herber's explanation distinguishes his work from many other role-playing games in which the goal is to develop characters and acquire power and/or wealth. In contrast, characters in Herber's scenario are rewarded with mental instability.
The source is the essay-review on www.electronicbookreview.com written by Keith Herber.