What type of behavior is classified as delusional?

Delusional behavior is any action a person takes due to delusional beliefs. Examples of delusion behavior include stalking a celebrity because of an imagined romance or acting superior to other people because of an inflated ego.

The behaviors may be symptoms of delusional disorder, which is a psychiatric condition. People with delusional disorder may act overly jealous or persecute people they mistakenly believe are harmful. Some people with delusional disorder experience hallucinations, seeing or hearing something that does not exist in reality. Scientists don't know what causes delusional disorder, but researchers study the possible roles of genetic, biological and environmental factors.