A morbid fear which the patient realizes to be absurd but nevertheless is unable to explain and overcome is called:

Phobia:

• A phobia is a morbid on pathological fear which the patient realizes to be absurd but nevertheless is unable to explain and overcome it.
• You might have met or heard of someone who was afraid to travel in a lift or climb to the tenth floor of a building, or refused to enter a room if s/he saw a lizard. You may have also felt it yourself or seen a friend unable to speak a word of a well-memorised and rehearsed speech before an audience. These kinds of fears are termed as phobias.
• People who have phobias have irrational fears related to specific objects, people, or situations.
• Phobias often develop gradually or begin with a generalised anxiety disorder.
• Phobias can be grouped into three main types, i.e. specific phobias, social phobias, and agoraphobia

Additional Information

Mania:

• People suffering from mania become euphoric (‘high’), extremely active, excessively talkative, and easily distractible.
• Manic episodes rarely appear by themselves; they usually alternate with depression. Such a mood disorder, in which both mania and depression are alternately present, is sometimes interrupted by periods of normal mood. This is known as bipolar mood disorder.

Note: Paranoia is sub-type of schizophrenia.