5 scariest(and interesting) mental conditions

I have listed some of the mental conditions which i find  scary and interesting, its not in any kind of order:

1) Cotard's syndrome: It is a rare condition which makes people believe they are actually Dead. People suffering from this syndrome believe that they are dead,have never existed or have no inner organs. These people are completely fine otherwise,at least physically, but they believe that they are dead as strongly as you and I believe that we are alive

2) Capgras syndrome/Capgras delusion: It makes you believe that a person close to you has been replaced by an impostor.You will see your mother,father or spouse as they normally are but will not believe that it is actually them! You will be completely convinced that it not your loved one but someone pretending to be,no matter what they say or do.

3) Anton-Babinski syndrome: People with this syndrome are actually blind but they do not know that they are blind and will deny it if you ask them. They cant see a thing, they bump into walls, crash into furniture but they will not realize or admit it that they are actually blind. This condition is not perfectly understood but it seems to be related to strokes and head injuries.

4)Apotemnophillia: It makes a person who is really healthy want to cut off one of his own limbs. They don't look crazy,they will look completely rational and sane and they will be complete functional in society but on the side they not only want to chop off their hands and legs but often act on the desire. It is not completely known why this happens but neurologists believe that it is due to not having a complete body image map and the patient believes that the limp is not a part of his body.

5)Fatal familial insomnia: This one probably the srariest of them all. it is a genetic condition and once it kicks in it will make it impossible for your brain  to go to sleep. sleeping pills and sanatives do not work and people who are affected by it will stay awake until they die. Luckly it is a extreemly rare condition but it is scrary because it basically a nurological death sentance.
  The disease has four stages, taking 7 to 18 months to run its course:
1. The patient suffers increasing insomnia, resulting in panic attacks, paranoia, and phobias. This stage lasts for about four months.
2. Hallucinations and panic attacks become noticeable, continuing for about five months.
3. Complete inability to sleep is followed by rapid loss of weight. This lasts for about three months.
4. Dementia, during which the patient becomes unresponsive or mute over the course of six months. This is the final progression of the disease, after which death follows.