It's not shown at all, but if playing the Physician, you meet your first acquaintance by way of them being a patient in the hospital, who is mentioned to have a self-inflicted eye wound.
it's heavily implied in the no more ending that your character commits suicide and it's heavily implied that suicidal tendencies run in the bright young thing's family
The Priest and The Dancer legacies seem to include some type of dysmorphia, as well as uniquen ending for The Priest legacy. It's now shown or heavily described. You can summon minion (Raw Prophet) whose icons looks like mutilated limbs, but its not required for gameplay.
player choice - you can send winter followers to kill investigators, on failure they follow and watch without acting the player is watched as part of investigations but this is with their knowledge
The player character is mentioned as having a chronic illness in the Apostle Obsonate legacy - one of the reasons they followed the Long in the first place is that the Long's blood acts as a counter to the illness.
all characters can become mentally ill, the bright young thing's father is heavily implied to be mentally ill prior to their (unrelated) death, one of your followers can become badly mentally unwell and you can intentionally cause 2 characters to become mentally ill
To complete the game, one has to access the Spider's Door. This card has a simple silhouette of a spider on it, but I don't think there's anything other than that.
If you play The Dancer legacy, you can get cards with simple snake silhouette and there are mentions of 'snakes entering the body', though it can be metaphorical.
There are also snakes on The Priest unique victory card.
Not fingers, but a hand. The 'An Injury' card shows a hand with a bloody hole in it, but is more representative of a general work-related injury than what it's probably depicting.
One of the obstacles you can encounter are the Fretful Dead. These are plainly ghosts, and are described as well as have a little icon. Places with them are: Keglin's Scratch, Forman House, Voivode's Citadel, Mausoleum of Wolves, Snow's Keeper, Miah, and Fort Geryk.
I don't consider this a jumpscare, but if you're first playing the game and unprepared, the sudden shift to the Mansus from the main board and back again can be incredibly jarring.
Not exactly, there's Dread card described as 'seeing too much' and if you have too many of them you can fall into Despair (which sounds description-wise as clinical depression) and lose the game. Attack-per-se is not present.
This is implied your character commits suicide if you let three Dread cards accumulate when Bleak Thoughts is active, resulting in a game over titled as Despair.