I suggest that if they lose 1/10th of their current SAN in one go they gain a temporary insanity, such as short-term catatonia, nightmares or a phobia. When their SAN reaches 0, they're hopelessly lost. SAN can be regained through therapy, rest and weak tea.

This would work as a substitute:

If the character encounters something that is likely to threaten their sanity (a rotting corpse, a vampire, a dragon, Great Cthulhu, etc), the player rolls d100. If the result exceeds their current SAN, they roll another dice (usually a d6, though more - many more! - for particularly frightening sights) and deduct that amount from their SAN.

I suggest that if they lose 1/10th of their current SAN in one go they gain a temporary insanity, such as short-term catatonia, nightmares or a phobia. When their SAN reaches 0, they're hopelessly lost. SAN can be regained through therapy, rest and weak tea.

For example: Matt Warren, Occult P.I. has a MIND of 16, so his SAN is 80 at the start of the campaign. His first case involves a series of bodies that have been discovered with their lips and eyelids sewn shut with red thread. He's in the morgue, and on his first sight of the bodies makes a SAN check, getting a 92 for the result. He rolls a d6 and gets a 4, meaning his SAN is now 76.

And thus begins the slow descent into madness.............

Not everyone plays Call of Cthulhu.

Please expand upon your idea and explain how Sanity checks work.

Thanks!