It is not accurate to say that "many" people with mental illnesses believe they are Jesus Christ, but there have been cases reported of individuals experiencing such delusions. The belief of being a religious or historical figure, like Jesus Christ, is a specific type of delusion known as "grandiose delusion" or "delusion of grandeur."
Delusions of grandeur can occur in various mental illnesses, most commonly in conditions like schizophrenia, bipolar disorder, and certain forms of psychosis. People experiencing this type of delusion may firmly believe that they possess special powers, abilities, or identities, often associated with prominent historical, religious, or influential figures.
While such cases exist, it's crucial to emphasize that mental illnesses are complex and varied. Most people with mental health conditions do not have delusions of grandeur or believe they are historical or religious figures.
It's essential to approach discussions about mental health with sensitivity, understanding, and empathy. If you or someone you know is struggling with mental health issues, seeking professional help from a qualified mental health practitioner is advisable. They can provide appropriate support, diagnosis, and treatment.