These are my house rules for handling Sanity in Call of Cthulhu 7e. Most of the rules are not strictly speaking new rules; the mechanics basically work the same. However, I have rewritten and clarified the fluff, and made some things simpler. I believe my changes make the sanity system into a simple yet flexible system for handling trauma.
In my version, the Call of Cthulhu sanity system specifically handles trauma. Characters who have other neurodivergences do not start with a lower sanity score. Their experiences are roleplayed out and do not interact with the Sanity system. (This includes characters with compulsions, fears, anxieties, or addictions which are not caused by trauma.)
Conversely, traumatized characters may begin with Phobias or Manias at the start of the game. (I have chosen to capitalize Phobia and Mania when referring to the game mechanics, so that they are clearly different from phobias and manias the mental health conditions.)
The Call of Cthulhu states that you can lose Sanity from non-Mythos sources, but does not provide guidance about how much Sanity you lose from various non-Mythos sources. I drew inspiration from Trail of Cthulhu’s Stability system to create the following chart (before the slash is Sanity loss on a success, after is Sanity loss on a failure):
0/1D2: Find mutilated animal corpse.
0/1D3: Find corpse or body part; witness a killing.
1/1D3: A human being tries to harm you; car accident; witness torture; psychotic break not caused by insanity.
0/1D4: Non-threatening omens; grisly corpse or crime scene; human being attacks you with intent to kill; you kill someone in a fight.
0/1D4+1: See many corpses or a large battle; find out a loved one or Significant Person has died; week in solitary confinement; bitten by a vampire.
1/1D4+1: Kill someone in cold blood; torture someone; find the corpse of a loved one or Significant Person; attacked by a loved one or Significant Person (who wouldn’t attack you normally); threatening omen or magical effect.
0/1D6: Witness death of friend or Significant Person; torture someone for an hour or longer; discover you have committed accidental cannibalism; awaken trapped in a coffin; see “normal” supernatural creature (mi-go, deep one, ghoul, skeleton, etc); see Bast
0/1D6 +1: Talk to someone you know to be dead; be possessed by an outside force.
1/1D6+1: Witness gruesome death of friend or Significant Person; kill friend or Significant Person; undergo torture.
0/1D8: See Yig or a zombie; see a werewolf change shape.
0/1D10: Undergo severe torture.
1/1D10: See a corpse rise from its grave; see Father Dagon or Mother Hydra.
1D3/1D10: see Dark Young of Shub-Niggurath, Hound of Tindalos, King in Yellow, etc.
1D6/1D10: see shuggoth.
2/2D10+1: Witness giant severed head falling from the sky, or similar gruesome, incomprehensible, supernatural event.
1D3/1D20: see Gla’aki
1D10/1D100: See Great Cthulhu, Azathoth, Hastur, Nyaralathotep, Shub-Niggurath, etc.
Because of the increased number of things the PCs can lose sanity from, I have expanded monster sanity limits to apply to all discrete sources of sanity loss. (That is, in one scenario, you can lose no more than 4 Sanity from being attacked by a human with intent to kill.)
I think the list also helps calibrate exactly how bad seeing Mythos creatures are: even seeing a creature as relatively ordinary as a Deep One is as mind-scarring as torturing someone for more than an hour.
I typically give my players control over their actions when insane. While I would take over if they abused the privilege, I find that the depth and richness of playing an insane character more than compensates for the risk that a power gamer would declare themself to have a Phobia of oceans when the entire game takes place in the Sahara Desert.
Insanity in Call of Cthulhu has five mechanical effects: bouts of madness; Phobias and Manias; delusions; corruption of backstory elements; and different results of fumbles.
I do require my players to roll on the appropriate table to determine their behavior when they have a bout of madness. I think the loss of control helps cement the helplessness of insanity and (unlike the other insanity-related tables in the game) the bout of madness table is rather good.
Corrupting backstory elements also works well following the rules as written, although again I allow my players to corrupt their own backstory elements.
Phobias and Manias should not be understood as literal phobias and literal manias. The examples in the book are at best bland and at worst nonsensical. (Who responds to trauma by acquiring a special interest in trains?) Instead, we should understand a Phobia as anything that the character avoids because of their trauma, and a Mania as anything that the character seeks out because of their trauma.
Interpreted in this way, the Phobias and Manias system can accommodate a wide range of reactions to trauma depending on the experiences and personality of the individual character. Phobias do not all need to be fears: anorexia may be modeled mechanically as a Phobia of food, and hypersensitivity to noises may be modeled as a Phobia of loud noises. Some fears may be more conceptual than the ones presented in the book: for example, a religious character may have a Phobia of going to hell because of the evil deeds they have performed.
Similarly, a Mania can be any number of different things. Some Manias will be compulsive behavior, like rocking back and forth while muttering to yourself or being unable to stop writing out quotes from the Necronomicon on the walls. (Some compulsive behavior, like constant twitching, is in my opinion best handled through corruption of the Description backstory element.) Some Manias may be attempts to keep yourself safe: for example, a Mania for sitting with your back to the wall so no one can sneak up on you or a Mania for carrying a gun with you wherever you go. Other Manias may, again, be more conceptual: a Mania for making sure that everyone you love is safe, for example, or a Mania for being liked by everyone you encounter so they don’t hurt you, or a Mania for never making anyone angry. Some Manias may be coping mechanisms or ways to numb overwhelming feelings: for example, addictions, alcoholism, compulsive sex, self-harm, risky behavior such as skydiving or reckless driving, religion, or overspending are all good Manias.
Because of the diversity of potential Phobias and Manias, I suggest the Keeper or the player (whoever will be choosing the Phobia or Mania) spend some time in advance thinking about what Phobias or Manias are appropriate for the character, so that the game doesn’t stall while they’re trying to think of one immediately after seeing Great Cthulhu.
Delusions are one of the most fun rules in Call of Cthulhu. The Keeper is permitted to lie to the players about their characters’ perceptions and the results of rolls. I encourage Keepers to pay attention to the players’ corrupted backstory elements, Phobias, Manias, and the triggers of their insanity to figure out appropriate delusions. Do not consider yourself limited to the examples in the book, which mostly involve hallucinating Mythos horrors. Instead, consider: should a successful Psychology roll tell the PC that that NPC secretly hates them? Should that Spot Hidden check reveal that an unarmed stranger is secretly holding a gun? Should Listen enable you to overhear people talking behind your back? There are lots of excellent opportunities to mimic the cognitive distortions associated with untreated trauma.
Finally, insane characters receive different results on failed pushed rolls or on fumbles: a sane character who fumbles a Jump check might fall off the cliff, while an insane character will acquire a delusion that they can fly. This is profoundly stupid and in my opinion takes away from the somber and horrific tone of Call of Cthulhu. I am baffled about why traumatized people apparently cannot fall off cliffs. I suggest that the Keeper keep the character’s insanity in mind when deciding on results of a fumble or a failed pushed roll, but otherwise be willing to give the same results they do to a sane character.
Call of Cthulhu has an endearing and heartwarming faith in the capabilities of the 1920s psychiatric establishment to heal trauma. For this reason, I have modified the rules heavily.
In my interpretation, Psychoanalysis is no longer the skill of performing Freudian psychoanalysis on patients. Instead, Psychoanalysis is the skill of helping traumatized people recover from their trauma, usually learned through trial and error or personal experience. For this reason, Psychoanalysis is now an occupational skill for members of the clergy (replacing Listen). Many other characters may take Psychoanalysis with a reasonable justification: for example, the character who has Psychoanalysis in my current game is a Tarot card reader.
Similarly, indefinite insanity is no longer cured by spending time in asylums or under psychiatric care. Instead, indefinite insanity is cured by spending a month in a quiet, safe, comfortable location where nothing especially stressful happens. This may be an asylum, if the asylum is doing its job; however, your house back at home is just as good.
I didn’t change the rules for backstory connections, but I’d like to express how much I like them as a way of modeling recovery from trauma. The PCs regain sanity (that is, coping ability) through spending time with things and people that matter to them. The system reflects the diversity that actual traumatized people have in their self-care techniques: I have PCs that regain sanity from telling stories, performing corde lisse, playing music, talking to their brother, and curling up in a corner while wearing a very large jacket with lots of pockets. There are really great roleplaying opportunities in the PCs responding to experiencing violence by each seeking out their own tools for self-care.
But as you become more traumatized, these supports become more difficult for you to access. You’re more likely to fail rolls to recover sanity if your sanity is already low, and the corruption of your backstory elements means you have fewer and fewer things you can really rely on to comfort you. Experiencing extreme trauma can force you into a cycle it is hard to escape from.
Normally, in Call of Cthulhu, you automatically lose sanity as soon as you read a tome. However, I am running a version of the Alexandrian Remix of Eternal Lies adapted to Call of Cthulhu. (Players, DO NOT click that link.) In this remix, the characters are supposed to read sixteen books. Following the rules as written, reading sixteen Mythos tomes is going to drive even the sanest PCs mad from the revelation, which makes the remix unplayable.
The fix is simple. Tomes now function like any other source of sanity loss, and you make a Sanity check every time you read them. The Sanity loss given in the Keeper’s Handbook is the Sanity you lose on a failed check. However, if you study a tome fully during downtime, you will automatically lose the Sanity cost of reading it.
Following the Alexandrian’s example, I incentivized my PCs rereading the tomes by giving them bonus dice to certain Library Use and other research rolls when consulting particular tomes. (For example, a tome about Nyarlathotep might give you a bonus die to all research involving Nyarlathotep.) The most powerful tomes with the most useful bonus dice have the highest Sanity loss.
To adapt the Trail of Cthulhu tome rules to Call of Cthulhu, I implemented a ‘skimming’ rule. If the PCs skim a book, they make a Sanity check, get a handout with a general sense of the book’s contents, and usually know which research rolls they would get bonus dice to by consulting it. However, they do not gain Cthulhu Mythos or spells, which require further study and loss of SAN.