9 Terrifying Diseases That Turn Your Life Into A Horror Movie

5. Capgras Delusion

Invasion of the Body Snatchers is freaky enough without the possibility that it could actually come true. Imagine that one day, you slowly began to realise that the people around you had been replaced by a doppelganger. Your loved ones certainly all look the same, but you just know that there's something not right with them.

What's more, everyone else seems to be in on it, insisting that they're the same as they always were, trying to convince you that these pod people are actually your friends.

This is what happens to those under the influence of the Capgras Delusion. Sufferers will often become convinced that someone close to them has been replaced by an identical looking impostor. Sometimes, these impersonators are benign, but sometimes they are an "evil version" of the person they replaced.