30 Scary Mental Illnesses You Won’t Wish On Your Worst Enemy

Jumping Frenchmen of Maine is a rare disorder of unknown origin. Some affected individuals may exhibit automatic or “forced” obedience after a startle response during which they automatically respond to simple commands such as jump, run or hit. Individuals with this condition were first found in the Moosehead Lake region of Maine. One theory is that it is a genetic condition.

Similar to paranoia, a person suffering from pronoia feels that persons or entities are conspiring against them, but instead of feeling that the world is conspiring to harm them or do them bad, people with pronoia feel that the world around them conspires to do them good.

Anton–Babinski syndrome is mostly seen following a stroke or head injury. Those who have it become completely blind as a result of the injury, but often are quite adamant in the face of clear evidence of their blindness that they are capable of seeing. They employ confabulation to fill in the missing sensory input. Following the accident, it may take days or weeks for doctors and family members of the victim to realize that the patient is blind. The patient will collide with pieces of furniture, fall over objects, may try to walk through a wall or through a closed door or talk to people who aren’t there at all.

Olfactory reference syndrome is a mental disorder in which there is a persistent, false belief and preoccupation about emitting abnormal body odor which is foul and offensive to other people. People with this condition often misinterpret others' behaviors, e.g. sniffing, touching nose or opening a window, as being referential to an unpleasant body odor which in reality is non-existent and cannot be detected by other people.

Erotomania is a type of delusional disorder in which the affected person believes that another person is infatuated with him or her. This disorder is most often seen (though not exclusively) in female patients that are shy, dependent, and sexually inexperienced. The object of the delusion is typically a male who is unattainable due to high social or financial status, marriage, or disinterest.

Men can experience some of the same symptoms of pregnancy as an expectant partner. These most often include minor weight gain, altered hormone levels, morning nausea, and disturbed sleep patterns. In more extreme cases, they can experience labor pains, postpartum depression, and nosebleeds. This condition is known as Couvade Syndrome or sympathetic pregnancy.

Pretending to have a mental disorder is still a mental disorder. It is called nonsense syndrome or Ganser syndrome or prison psychosis. People affected by it exhibit short-term episodes of odd behavior similar to that shown by people with other serious mental illnesses. It is often seen in prison inmates where it may be seen as an attempt to gain leniency from prison or court officials.

Aboulomania is a disorder that involves the occasional onset of crippling indecision. People suffering from it otherwise have no physical and mental problems. They simply run into very serious problems whenever they’re faced with certain choices even with simple everyday tasks (going for a walk or not, paper or plastic), to the extent that they struggle to regain normal function. They feel imprisoned by the inability to fulfill their own will.

There exists a clinical condition that is the opposite of anorexia called Bigorexia. The person affected by it becomes obsessed with the idea that their body is too small, too skinny, insufficiently muscular, or insufficiently lean, although in most cases, the individual's build is normal or even exceptionally large and muscular already. It affects mostly males, particularly those involved in sports where body size or weight are competitive factors.

There’s a phenomenon called the "Paris syndrome" which mostly affects Japanese tourists who are visiting Paris for the first time. It is caused by the disparity between the Paris shown in Japanese media and the real Paris. Symptoms include hallucinations, delusions, and feelings of persecution. There is even a 24-hour helpline run by the Japanese embassy in Paris to help these tourists.