The two are clearly distinguished in psychological literature. People suffering from ideas of reference experience intrusive thoughts of this nature, but crucially, they realize that these ideas are not real. Those suffering from delusions of reference believe that these ideas are true.^{[citation needed]}

In their strongest form, they are considered to be a sign of mental illness and form part of a delusional, paranoid or psychotic illness (such as schizophrenia or delusional disorder).

They may include experiences such as:

• feeling that people on television or radio are talking about, or talking directly to them
• believing that headlines or stories in newspapers are written especially for them
• having the experience that people (often strangers) drop hints or say things about them behind their back
• believing that events (even world events) have been deliberately contrived for them, or have special personal significance
• seeing objects or events as being deliberately set up to convey a special or particular meaning