"It has been reported that some victims of violence, during the act, would retreat into a fantasy world from which they could not WAKE UP. In this catatonic state, the victim lived in a world just like their normal one, except they weren't being raped. The only way that they realized they needed to WAKE UP was a note they found in their fantasy world. It would tell them about their condition, and tell them to WAKE UP. Even then, it would often take months until they were ready to discard their fantasy world and PLEASE WAKE UP."
SCP-532 was a stream of sentient, telepathic, serial killing raw sewage that the SCP Foundation couldn't contain at all. Once you've been selected as its next target, it follows you everywhere, injecting itself into every plumbing system you'll ever use. It will poison you to death and there's nothing you or anyone else can do about it, because it telepathically disguises itself as ordinary water. You could be drinking it, bathing in it, brushing your teeth with it, washing your dishes and clothes in it, eating food at a restaurant whose staff have washed their hands in it, etc., and you'd never know. No matter how sick you get, your doctor will never be able to figure out the cause.
SCP-157 can pretend to be your dinner... which then eats you, from the inside out.
Speaking of SCP paranoia, take SCP-288. When your 'beloved' significant other gets down on one knee, and proposes marriage, think twice before putting that ring on your finger.
SCP-280. Any time you're in darkness, it could be there, waiting for you. Any shadow you just spot out of the corner of your eye, could be it. Turn on the lights and its not there? Doesn't prove anything, it's just retreated, and it will come back if you turn them off again. Oh, and it needs to be kept in total darkness to keep it from escaping.
SCP-966, horrifying invisible creatures that prey upon humans. They stalk you and deprive you of sleep, and once you're weakened enough, they eat you. All the while you never notice that one of them is behind you. Not good to read about if you have insomnia. And it turns out that they're found wild all over the world.
Especially in two blacked-out locations, one of which have 5 blanks followed by 7. Very comforting for readers in N-o-r-t-h A-m-e-r-i-c-a. Or S-o-u-t-h A-m-e-r-i-c-a. Or... Oh Crap.
Forget all the SCPs. Forget the Sleep Killers, forget the sewage, forget the Eyes in the Dark, forget the botfly toothpicks and the statue that sneaks up behind you and snaps your neck. Now remember, anything can be a potential SCP. Even ideas can be lethal. Sleep tight.
In Dominion And Duchy there is a brief mention of an Large Hadron Collider on Earth, that is in the United States for some reason. When it is turned on, half the United States is glassed and something comes out that eats Venus!
Marble Hornets. Try watching entries 14 (Slendy comes into Alex's bedroom while he's asleep) and 19 (The masked man does the same thing to J, who then disappears for three hours with no memory of what happened) and see if you can sleep easily after that. For that matter, the slightest glimpse of Slendy should be enough to freak you out, especially when you realise that he's in every video and you can't always see him... which means he could be anywhere. He could be watching you right now.
Don't bother asking your friends or family for help with your Slendy problems; chances are, they're working for him. And they have been all along.
That guy you see in class every day who helps you with your homework? He's the one sending you threatening messages and sneaking into your room at night. He belongs to a cadre of Slenderminions—and he's helping to orchestrate your forced induction into their circle.
In "Mary Asher Phone Call", Noah learns that the Collective has had its eye on him since birth, and has been monitoring his every move throughout his entire life. Oh... and they're in his house watching him at that very moment. Try getting a good night's sleep after that.
What isthe Terrible Secret of Space? What could be so bad that the Space Robots need to push the humans down the stairs for their own protection? What does bread have to do with it? Is the Shover robot malfunctioning like the Pusher robot says? Is it the other way around? Are they both malfunctioning? Are they lying about the Terrible Secret? Are they the Terrible Secret?!
This will make you paranoid of plushies. Especially big ones, although the small ones are still paranoia-worthy.
The Entity of Atop the Fourth Wall. The Entity will abduct you if you are alone. Being in a house with someone in the next room counts as alone. Being in a room with someone around the corner counts as alone. At one point, being in the room with someone looking the opposite direction counted as alone. Sweet dreams.
No she's not an Eldritch Abomination, but The Nostalgia Chick's behavior towards Todd creates a more realistic fear. A crazed stalker who will do everything in her power to get what she wants, including kidnapping, government fraud, blackmail and plenty of sexual harassment.