That expression is a residue of the absurd belief during the Middle Ages that mental illness is caused by evil spirits—that justified burning the afflicted person at the stake. (Remember Joan of Arc?)
This ignorant, even maliciously unscientific, portrayal of psychiatric symptoms is an appalling disservice to all our patients who struggle with a potentially disabling neuropsychiatric disorder. Regrettably, some religious entities still propagate the fallacy of possession by an evil spirit and call for exorcism of bizarre behaviors sometimes associated with psychosis.1 What is really needed is an exorcism of unscientific and harmful misconceptions that mental illness is the nefarious work of Beelzebub or Lucifer.
Strange manifestations beget weird explanations
I can understand how ignorance about the neurologic basis of unusual delusions and behavior can trigger absurd religious explanations for their cause. Sometimes, brain pathology can have strange clinical manifestations that are beyond the ken of the average layperson, which invites metaphysical, religious, or philosophical explanation. Here are examples of neuropsychiatric symptoms in the category of “very unusual” that might summon a demonic malfeasance.
Delusion of possession or alien control. Some people complain of being possessed2; delusional people who have a strong religious background might believe they are possessed by Satan himself. Some of my patients with psychotic depression believe this, expressing great guilt and anguish about being doomed to go to Hell.
Alternately, patients with schizophrenia often think they are under the control of an “alien force” that shapes their behavior, feelings, and thoughts (a Schneiderian first-rank symptom). In a 2012 editorial, I proposed that this “alien intruder” is the unintegrated right hemispheric consciousness,3 and that disintegration of the 200 million inter-hemispheric white matter fibers of the corpus callosum might be the cause of the loss of integration of the right hemisphere into the dominant left hemisphere.
Some people attribute external control on their lives to a government agency, a foreign country, or a spiteful neighbor; others believe it is the work of evil spirits. Whereas the foundation of the delusion is brain pathology, the content of the delusion is colored by the affected person’s cultural and religious background.
Apotemnophilia. A neurologic disorder that manifests in a bizarre clinical symptom that invites faulty explanation: A person demands amputation of a leg because “it doesn’t belong to my body.”4 The cause of this strange and confusing disorder has been misinterpreted as a paraphilia, a desire by the affected person to achieve greater sexual satisfaction by having a stump. It was first reported in the September/October 1972 issue of the magazine Penthouse, where it was described as the motivation to heighten one’s sexual appeal because stumps can be sexually exciting to their partners.
It took many years of neurologic research to demonstrate that apotemnophilia is caused by pathology in the parietal lobe, where the physical representation of the body is located. Incomplete neurodevelopment of the parietal lobe can cause a person to fail to recognize a leg as a “legitimate” part of his body, and he (she) then desperately seeks amputation of the so-called alien limb (see the description of xenomelia below) that is attached to his body.
When an affected person is asked to delineate the borders of an alien limb, he draws a line on the skin at the precise border between the alien limb and the rest of his body—where the amputation should take place. Requests for surgical amputation were adamantly denied when the disorder was thought to be a weird sexual practice, but elective amputation in the context of neuropsychopathology is seriously debated now—and has, in fact, been reported.5 The term “body impaired integrity disorder” has been proposed, but neurologists consider the disorder an example of xenomelia.
Xenomelia (‘alien limb syndrome’). An odd neurologic disorder produced by brain pathology, in which a person has a sense of estrangement about 1 or more limbs.5 The disorder can be caused by a neurologic lesion such as tumor, Creutzfeldt-Jakob disease, hereditary diffuse leukoencephalopathy, demyelinating disease, progressive dementia, corpus callosotomy, intracerebral hemorrhage, or thalamic degeneration.6
So-called “alien hand syndrome,” or asomatognosia, is a widely recognized example of xenomelia, and is associated with medial frontal lobe damage.
Another variant of xenomelia is somatoparaphrenia, unawareness of a part of one’s body.7
Cotard syndrome. A nihilistic delusion of the nonexistence or dissolution of a body part; in extreme form, the delusion of being dead or nonexistent.8 The syndrome sometimes occurs in the setting of severe depression. Research has shown an association with atrophy of the insula,9 which is responsible for internal proprioception (interoception).
Delusional misidentification syndrome. A set of neuropsychiatric conditions in which a person misidentifies people, places, objects, or events10: