Paranoiac (noun)

A person suffering from paranoia, a mental disorder characterized by delusions of persecution, unwarranted jealousy, or exaggerated self-importance.

Origin:

From late latin paranoicus, from greek paranoiakos 'of madness, paranoid', from paranoia 'madness'.

Examples:

1. The paranoiac believed that everyone was out to get them and constantly looked over their shoulder.
2. Paranoia is a serious mental health issue, requiring professional help and treatment.
3. The paranoiac's delusions of grandeur made it difficult for them to have meaningful relationships with others.
4. The psychologist diagnosed the patient as a paranoiac, based on their persistent and irrational beliefs.
5. Paranoia can lead to isolation, anxiety, and depression, negatively impacting a person's quality of life.