A<unk>  is a<unk> al state that only concerns one particular topic. This is contrasted by what is sometimes called multi-thematic or polythematic<unk> s where the person has a range of<unk> s (typically the case of schizophrenia). These disorders can occur within the context of schizophrenia or dementia or they can occur without any other signs of mental illness. Usually when these disorders are found outside the context of mental illness, they are often caused by organic disfunction as a result of traumatic brain injury, stroke, or neurological illness.
People who suffer from these<unk> s as a result of organic disfunction often do not suffer from any obvious intellectual deficiency nor do they have any other symptoms. Additionally, a few of these people even have some awareness that their beliefs are bizarre, yet they cannot be persuaded that their beliefs are false.
Monothematic delusion
Homicidal ideation
Cotard delusion
Labile affect
Suicidal ideation
Schizotypy
Capgras delusion
Mirrored self-misidentification