Is there a mental illness When person believes their lies?

The belief that one's lies are the truth is often associated with a mental illness known as confabulation. Confabulation is a symptom that is often observed in individuals with damage to the frontal lobes, which are involved in memory and decision-making. People with confabulation may sincerely believe in the unreal or imagined events they describe, and they may not be aware of the fact that they are not truthful. It's important to note that confabulation is not the same as lying, which is the intentional act of deceiving someone. Confabulation is considered a symptom of a medical condition or cognitive impairment, while lying is a conscious and purposeful action.